Honestly, I immediately thought of the tv series Merlin. Then, because of Arthur showing up in season 5, I thought of Once Upon a Time. That would totally be the easy way out, though - and we know I don't like those.
Thor from Marvel (any of probably a dozen, but the one I know the best is from the movies)
With that 'if he be worthy' stuff on Mjolnir, I figure if there's anyone - besides the prophesied - king that would be able to simply pull the sword out, it'd be him.
Hessler from Rogues of the Republic (series) by Patrick Weekes
(Pretty sure he's the one in the pointy hat.)
Hessler is a self-titled Master Illusionist. Honestly, I can't think of any skill more important than this, because if I found the sword in the stone, I'd definitely want someone to keep the lookie lous and enemies off our backs. (Or, better yet, not even knowing that we found it.)
Belle from Beauty & the Beast
Honestly, without someone with a high level of intelligence, I think there's a high probability of this whole thing falling apart through some stupid reason. (Like I lost the map and can't find the way back after I assemble my team.) Besides which, with all those books of hers, she might be able to create a compound that'll melt the stone but leave the sword unharmed. And she's one of the few brains that I don't think would be adverse to a bit of adventure.
Erik Lehnsherr from X-Men
Okay, so I think he'd be useful to have around for this - maybe even could slide the sword right out, yeah? But... I totally don't see him just handing it over afterwards. So, the sword would be out but I might have just given Magneto even more power. (And say whatever you will, Ian McKellen will always be Magneto in my mind.)
And, when all else fails (because, seriously, with this crew, it will):
Vinny from Atlantis: The Lost Empire
We blow that stone up! Though, knowing me, I'd probably just start there. :)