Some more examples, from probably the oldest Arthurian text there is (c. 1100):
-Hen Beddestyr, who could outrun horses
-Hen Was the Swift, who could outrun any four-footed creature
-Sgilti Light Foot, who could run over treetops and over reeds without bending them
-Drem ap Dremidydd, who from Cornwall ‘could see a gnat rise with the sun’ in Scotland (presumably this is an example and he had really good eyesight, but possibly his special power was just that he was really good at seeing a specific gnat)
-Menw ap Teirwaedd, who was a magician and could cast invisibility on his entire party (possibly only effective against pagans) and placate animals (specifically by magic)
-Osla Big Knife, who may not have been magic himself but if he laid his knife across a river in its sheath it would form a bridge large enough to carry all of the armies of Britain
-Gilla Stag Shank, who could leap three hundred acres at once ‘and who was the chief leaper of Ireland’ (good for you, dude)
-Sol, who could stand all day on one foot
-Gwadyn Osol, who could flatten mountains by standing on them
-Gwadyn Oddeith, whose soles got really hot and threw off sparks whenever he hit something hard (a bit less useful than Gwadyn Osol)
-Sugyn ap Sugynedydd, ‘who could suck up a sea on which there were three hundred ships until it was nothing but a dry strand’
-Cacamwri (possibly just a servant rather than an actual warrior), who was really good at destroying barns
-Gwefyl ap Gwastad, who when he was sad could stretch his upper lip over his head and hide under it
-Uchdryd Cross Beard, who could throw his beard over ‘fifty rafters in Arthur’s hall’
-Clust ap Clustveinydd, who ‘were he buried seven fathoms in the earth he would hear an ant stirring from its bed in the morning fifty miles away’
-Medyr ap Medyredydd, who could hit a wren in Ireland from where he was in Cornwall ‘through both legs’ (unclear if these are the wren’s legs or his)
-Gwiawn Cat Eye, ‘who could cut a corner from a gnat’s eye without harming the eye’
-Special mention to people who may not have had superpowers of any kind: Sanddef Angel Face, (so beautiful that no one attacked him at Camlann because they assumed he must be an angel), Morfran ap Tegid, (so ugly that no one attacked him at Camlann because they assumed he must be a demon), Canhastyr Hundred Hands (supposedly has a magic collar), Cors Hundred Claws (supposedly has a magic leash) (I assume they got along very well), Llwch Windy Hand and Samson Dry Lip (no explanation of these last four epithets so perhaps they don’t actually have any supernatural powers), and Gwydden the Difficult, who was probably just a dick
(I’ve included only highlights; I should point out that this list is eight pages long in the Penguin edition I have on hand. And for fairness’s sake I should probably also add that this list is not to be taken seriously since the story it’s included in is probably a parody, though it is also where Kay’s powers mentioned in the original post originate from, and Gwrhyr’s, who as far as I know only appears in this story.)
(Another delightful note is that Kay uses his magic heat powers in this story to keep the rain off his stuff and start fires ‘when his companions were cold’)
