• Red String of Fate: They meet because they say the same thing to the same person.
• Meet Cute: They do not just meet, the have an extraordinary meeting. Sherlock deduces many things about John at first sight and John is completely amazed, then Sherlock dashes away and winks in a very cute way, leaving John standing there, shocked. As John puts it on his blog “He was charming.” His sister and his friend start commenting on said entry about the gayness of the whole thing. In TAB a meet cute is presented again with an equally extraordinary meeting in which in addition the viewers are shown how much Sherlock and John connect when the latter catches the cane the former throws at him.
• Rescue Romance and Samaritan Relationship Starter : John saves Sherlock’s live while he was about to swallow the pill from the cabbie. Sherlock deduces John has killed a man who was trying to kill him and his positively surprised. Sherlock immediately asks John out to dinner. The acting is also suggestive of romantic interest as documented inside the Unresolved Sexual Tension trope (particular movements of the mouth, standing in front of each other and sharing long stares). In TAB we have another rescue operated by John which ends with the two of them flirting and the enemy remarking on that.
• Just Friends: John insist they are just friends, but no one seems to believe him. When this trope is not intended and they are really just friends, there is no reason to repeatedly bring up the tension by suggesting that they are not. MRS HUDSON: There’s another bedroom upstairs if you’ll be needing two bedrooms. MYCROFT: Might we expect a happy announcement by the end of the week? JEANETTE: You’re a great boyfriend. JOHN: Okay, that’s good. I mean, I always thought I was great. JEANETTE: And Sherlock Holmes is a very lucky man. BILLY: That’s not true. He’s a snorer. GARY: Hey, sht! BILLY: Is yours a snorer? For more examples see the Not a Date and She Is Not My Girlfriend subtropes.
• Not a Date: John practically says this out loud two times and Angelo doesn’t believe him.   ANGELO: On the house, for you and for your date. SHERLOCK: Do you want to eat? JOHN: I’m not his date. ANGELO: I’ll get a candle for the table. It’s more romantic. JOHN: I’m not his date!
• She Is Not My Girlfriend: Another romantic trope John cries out loud several times. And no one believes him. Again, it’s a common trope to increase the romantic tension, there’s no other reason to repeat it as the show goes on. DONOVAN: Opposites attract, I suppose. JOHN: No, we’re not …   *dramatic music* IRENE: Are you jealous? JOHN: We’re not a couple. IRENE: Yes you are. There “I’m not dead. Let’s have dinner.” JOHN: Who the hell knows about Sherlock Holmes, but, for the record, if anyone out there still cares, I’m not actually gay. IRENE: Well, I am. Look at us both. GARY: Eh, sorry we couldn’t do a double room for you boys. JOHN: That’s fine. We-we’re not… MRS HUDSON: You really have moved on, haven’t you? JOHN: Mrs Hudson! How many times …? Sherlock was not my boyfriend.
• Love You and Everybody: Both Sherlock and John use the ambiguous verb “to love” and Mary to deflect the declaration. JOHN: I want to be up there with the two people that I love and care about most in the world. SHERLOCK: Yes. JOHN: So, Mary Morstan… SHERLOCK: Yes. JOHN: and… you. SHERLOCK: Today you sit between the woman you have made your wife and the man you have saved – in short, the two people who love you most in all this world. 
• Everyone Can See It: Everyone thinks they are a couple. 
• Will They or Won’t They?: This is what part of the fandom is wondering and, when then this trope is used, usually the answer is “They will”, because fans are emotionally invested. BBC Three wonders it too: “#Sherlock and Watson Will they won’t they… solve some crime? Elementary! #TellyHaikus” Source
• Dance of Romance and Convenient Slow Dance: Sherlock and John have already danced off screen, specifically to a waltz and many times. Sherlock also declared that he loves to dance and lives in the hope of the right case, but he is the only one who doesn’t get to do it at the wedding (so might see him/them dance on screen in the future). Their dancing lessons are mentioned again in TAB, as Sherlock is thinking about them. They also make an easter egg appearance in the papers.
• Held Gaze: Sherlock and John share intense looks.
• Both staring at each other: PICTURE PICTURE PICTURE PICTURE
• Looks from Sherlock: PICTURE PICTURE PICTURE
• Unresolved Sexual Tension: The gaze and touch each other and there is tension about it. TV shows don’t code friends with tension. 
• Sherlock and John touching: PICTURE PICTURE PICTURE PICTURE PICTURE PICTURE PICTURE PICTURE PICTURE PICTURE
• Other moments that create sexual tension: PICTURE PICTURE PICTURE This two specifically have Sherlock and John taking turn at opening legs. PICTURE PICTURE
• Most moments under the Held Gaze trope.
• Comments on each other’s looks: JOHN: You being all mysterious with your cheekbones and turning your coat collar up so you look cool. (At the start of the episode John expresses this opinion with a look too and Sherlock replies aloud.) SHERLOCK: I prefer my doctors clean-shaven.
• Often staying very close in front of each other while talking.
• Moment Killer: They are drunk and are starting to act a bit too intimate with each other, where would that have gone without Tessa interrupting them? Do you ever wonder if there was a reason for that scene to end with an interruption?
• Operation Jealousy: Sherlock enters a fake romantic relationship and doesn’t tell John for a while. John looks surprised, but also jealous. He certainly doesn’t look happy about it.
• Romantic False Lead: John’s wife presented like a romantic lead, but the first time we see them after their marriage John and Mary are annoyed at each other. Mary is then revealed to have lied about everything in their relationship and to be an assassin. In The Abominable Bride, in Sherlock’s mind, their marriage is presented again as falling apart. Watson directly forgets that he has a wife and goes away with Sherlock, so that Mary has to go to great lengths just to see her husband, who, as Sherlock remarks, had abandoned her for himself. Sherlock even imagines they have a row. John is again disinterested in her while he leaves to go to the morgue. Later there is a whole scene in which it is shown that they are never at home together and barely see each other, despite being married. Sherlock instead gets a girlfriend, but it’s a fake relationship.
• Wrong Guy First: John’s wife is actually an assassin that has lied to him since the start of their relationship and shoots Sherlock, who is declared dead on the operating table, but he comes back to live because John is in danger. There is speculation that in the next series she could be made even more of a villain.
• Sleep Cute: John and Sherlock sleeping on the stairs.
• Literally Falling In Love: John looses balance and his hand lands on Sherlock’s knee. They both say they don’t mind.
• Aborted Declaration of Love: Sherlock wanted to confess something to John before going inside the plane, but made a joke instead. He had already confessed his feelings of friendship at the wedding.
• I Want My Beloved to Be Happy: Sherlock sacrifices himself so that John can have a family with Mary and their baby.
• Unrequited Love Switcheroo: In Series 1 and 2 we see John potentially emotionally interested, but Sherlock has turned him down from the start. John deals with the fact that Sherlock is not looking for a relationship and his interest is unrequited. In Series 3 Sherlock is finally ready to be emotionally involved, but John has found a new love interest, which is a romantic false lead anyway. Sherlock deals with having lost John forever.
• I Have Your Girlfriend: Moriarty kidnaps John at the pool. Magnussen kidnaps John and puts him in a fire.
• Second Act Break Up: At the end of Series 2 they are separated for two years.
• Break His Heart to Save Him: Sherlock makes John believe that he’s dead for two years in order to save his life.

• Accidental Hand Hold: John and Sherlock hold hands while trying run away from the police.
• Act of True Love: Sherlock jumps from a building for John, he says he would have jumped even if he couldn’t survive. Sherlock come back to live after being declared dead on the operating table because John is in danger. The only vow Sherlock will ever make in his life is to protect John’s family. Sherlock kills a man and goes to an exile which will lead to his death to protect John’s family.
• Anger Born of Worry: John shows anger both in The Last Vow and in Sherlock’s mind palace in The Abominable Bride because of Sherlock’s drug use.
• Betty and Veronica: John between Mary and Sherlock before it’s revealed that Mary is an assassin.
• Cardiovascular Love: There’s a heart between John and Sherlock when they are talking in front of the fire at the inn in The Hounds of Baskerville and there is another heart nearby. There are other possibly intentional easter eggs hearts.
• Declaration of Protection: Sherlock’s last and only vow.
• Finishing Each Other’s Sentences: In The Empty Hearse, there’s a whole montage of Sherlock and John finishing each other sentences. In The Sign of Three. SHERLOCK: Don’t compromise the integrity of the… JOHN: …crime scene! Full meta
• Love Triangle: John’s attention is contended between Mary and Sherlock in The Sign of Three, where, thought the two are on good terms, Sherlock get very sad about loosing John. We get a visual love triangle here. The are also several parallels between Sherlock and the bride: - John in front of Sherlock on one knee (during the knee grope). - John asking him the big question. - Sherlock being the other person who changed John’s life. - Sherlock being the other person John loves the most. - Sherlock organizing the marriage. - Sherlock dressing exactly like the groom. - Sherlock thinking he should be in the photo outside of the church, before he’s told to move away from the bride and the groom. - Sherlock waltzing with the groom. - Sherlock making a vow. - Sherlock throwing a bouquet. The wedding episode is even titled The Sign of Three, and, as the baby is only mentioned at the end, the episode are usually titled after what happens in them and the episode is about Sherlock’s coping with the wedding, it might as well be that they named it after the love triangle, especially singe soon after the mention of “The Sign of Three” we get this line referred to Sherlock, John and Mary: JOHN: Well, we can’t all three dance. There are limits! At the start of The Last Vow is clear that the current arrangement is making everybody unhappy, with John dreaming of Sherlock, Mary annoyed at John being so focused on a Sherlock that is not even there and Sherlock relapsing into his drug use. In The Abominable Bride an uncomfortable situation is presented again, with Mary and John’s marriage on a strain and Sherlock missing John when they are not together. An exchange is also completely dedicated to this triangle, with Sherlock and Mary being next to each other, John saying to Mary that he thought they were loosing each other and Sherlock replying instead that it is him who moved out.
• Not What It Looks Like: John catches Irene naked on Sherlock’s lap. Later he thinks there is some mutual attraction between them or that something is going on. Irene clarifies to him that he wasn’t even replying to her texts and that they are the couple.
• Shipper on Deck: Mrs. Husdon, Angelo and Irene Adler ship them a lot, they insist they are a couple or that they love each other. Molly and Mycroft seem to believe Sherlock has feelings for John. See all quotes under the Just Friends, Not a Date and She Is Not My Girlfriend tropes. More quotes for this trope: IRENE: Oh, and somebody loves you. Why, if I had to punch that face, I’d avoid your nose and teeth too. IRENE: There’s a back door. Better check it, Doctor Watson. IRENE’S TEXT: John’s blog is HILARIOUS. I think he likes you more than I do. MOLLY: You look sad when you think he [John] can’t see you. FRANKLAND: This is his PA! JOHN: PA? FRANKLAND: Well, live-in PA.
• There Is Only One Bed: There is an inversion of this trope, where they are mistaken for a couple and the owner of the inn apologizes for the lack of a double room. It serves the purpose of creating tension and remembering us that they look like a couple anyway. There is also the possibility that Sherlock might have tried to share a bed with John, since the owner acts like if he was asked a double room during the booking process and John informs us in his blog that Sherlock once proposed that they should sleep together in the same bed for a case.
• Green-Eyed Monster: John being jealous while Irene flirts with Sherlock. He counts how many messages she sends him, Irene herself says he’s jealous at the Battersea Power Station and he interrupts them with the baby names comment. Sherlock crashes John’s dates and treats his girlfriends very poorly until Mary, probably because after faking his death for two years he has to please John to be forgiven (plus she’s actually very clever, so he might really fancy her as a friend). After John finds Mary, Sherlock hears John in is head saying “Jealous?”, which is ambiguous in its relevance to his interaction with Molly and happen rights when Sherlock is obsessing over John not being there. Sherlock is jealous of Sholto.
• Get a Room!: Harry says this on John’s blog.
• Yawn and Reach: While drunk Sherlock puts his arm around John on the sofa.
• Double Entendre: John talks about it being rare for them to spend a time together like that talking (it’s night and they are alone) and puts a “man to man” there which makes uncomfortable a previously smiling Sherlock.
• Uncovering relationship status: John asks Sherlock if he has a girlfriend or a boyfriend, licks his lips, replies that “good” to the information that Sherlock is single and informs Sherlock that he is single too.
• Visual Innuendo:
• When Sherlock is removing the bomb from John in The Great Game, it is reminiscent of the blow job scene which Martin Freeman had in Love Actually. PICTURE
• During the stag night in The Sign of Three, Sherlock has liquid dripping from his mouth, a phallic object behind him and an object becoming shorter at the end of the scene in his hands. PICTURE Right after there is a transition of Sherlock fading inside John’s mouth. PICTURE

• In the Blind Banker Sherlock grabs John’s head in the dark and John probably thinks he’s going to kiss him.
• Sherlock equating their outings to a date: JOHN: Actually, I’ve, er, got a date. SHERLOCK: What? JOHN: It’s where two people who like each other go out and have fun. SHERLOCK: That’s what I was suggesting. JOHN: No it wasn’t … at least I hope not.
• John making sexual innuendo: JOHN: I’m glad no-one saw that. SHERLOCK: Hmm? JOHN: You, ripping my clothes off in a darkened swimming pool. People might talk.
• In A Scandal In Belgravia John looks at Sherlock’s crotch. PICTURE
• In A Scandal In Belgravia there is an almost naked Sherlock for John’s eyes. PICTURE
• Sherlock referring to him and John as “we” like if there was nobody else of importance in their life. SHERLOCK: Well, we’ll have to get rid of that. MYCROFT: “We”? MYCROFT: Why would he be? It’s been two years. He’s got on with his life. SHERLOCK: What life? I’ve been away. SHERLOCK: Just the two of us against the rest of the world. Full meta.
• John saying that he was “moving on” by marrying Mary.
• Magnussen identifies John as Sherlock’s damsel in distress, a generally romantic character.
• John asking to Sherlock “Am I pretty?” during the Rizla Game.
• Sherlock sadly looking at John’s chair. PICTURE
• Sherlock feeling strange at the wedding and calling Mycroft. Mycroft telling Sherlock that he told him not to get involved with John.
• In The Sign Of Three Sherlock glues John’s head on naked Vitruvian Man’s body (Visual Innuendo). PICTURE
• John dreaming of Sherlock while in bed with his wife. It’s the first thing we see him doing after the marriage.
• Sherlock calling Molly with John’s name in The Reichenbach Fall and in The Empty Hearse. Also thinking that John was there instead of Irene in A Scandal In Belgravia.
• After John’s marriage:
• Sherlock posts a weird entry on John’s blog, which sounds a bit jealous.
• Sherlock and John stop seeing each other. They hadn’t seen each other for a month and they met again only by chance.
• Sherlock removes John’s chair
• Sherlock starts doing drugs again.
• The shows tells us that John’s type is people like Sherlock when saying that that is the reason he likes Mary.
• Sherlock takes drugs before getting on the plane and knowing about Moriarty’s return and the probable conclusion is that he got high because he was leaving John, as he starts reading the story of how they met on John’s blog just after that.
• Sherlock being flirty and submissive with this line: HOLMES: Then correct me, Doctor. 
• Sherlock imagining John nagging him about his sexuality, proposing as possibilities one woman who the audience knows he has already refused and another who the audience knows he has talked well of only to insult the husband, while Sherlock acts shy about something that actually attracts him.
• Appearances of the God of Love: In the Unaired Pilot, when the “A Study in Pink” title appears there is a statue of cupid on screen. The Blind Banker it’s named after The Blind Archer by Doyle, which is about cupid. 

• Crush Filter: While Sherlock is on the roof looking for the suitcase.

• Visual Innuendo of Sherlock giving fellatio (without John): 
• In The Blind Banker he has a torch in his mouth. PICTURE
• In The Sign of Three he has his mouth full of cigarettes. PICTURE
• Visual Innuendo of John giving fellatio (without Sherlock): 
• In The Empty Hearse he has a torch in his mouth.  PICTURE 
• Visual Innuendo and hints of Sherlock bottoming: 
• Sherlock is show on all four with is bottom up in both The Sign of Three and the Unaired Pilot. PICTURE
• Double Entendre of Sherlock receiving fellatio: He imagines Moariarty lowering and sucking a gun in front of him, while some lines before… HOLMES: Sit down. MORIARTY: Why? What do you want?
• Double Entendre of Sherlock masturbating: MORIARTY: It’s a dangerous habit to finger loaded firearms in the pocket of one’s dressing gown.
• Double Entendre of Sherlock having sex with another man: MORIARTY: Let’s stop playing. We don’t need toys to kill each other. Where’s the intimacy in that?
• Does This Remind You of Anything? trope is used to enlighten two concepts tied to the scene with Moriarty in The Abominable Bride: 1) Sexual acts, fellatio in particular. 2) John as Moriarty uses this line: MORIARTY: There’s only one thing in this whole business that you find interesting. Which is associated with John: SHERLOCK: There was one feature, and only one feature, of interest in the whole of this baffling case, and quite frankly it was the usual. John Watson.   This is particularly relevant because before this scene, during The Abominable Bride, “feature of interest” is claimed to be often said by Holmes, while Holmes denies, rightly so, because he only says it once in the above line in relation to John Watson. This trope is also called in the dialogue: MORIARTY: Because doesn’t this remind you of another case?
• In The Empty Hearse John is fondling a man’s testicles for medical reason. Of all possible things they could have shown him doing, they show him do this (Visual Innuendo). PICTURE
• Or Are You Just Happy to See Me?: Used for both Sherlock and John towards other men. MORIARTY: Is that a British Army Browning L9A1 in your pocket or are you just pleased to see me? SHERLOCK: Both. *A man takes a bent phallic object from John’s trousers* JOHN: Doesn’t mean I’m not pleased to see you. MORIARTY: It’s a dangerous habit to finger loaded firearms in the pocket of one’s dressing gown. Or are you just pleased to see me?

It is what it is.