Steve Howe comes first to my mind at this moment.
http://www.youtube.com/watch?v=ZiA1XBXAE6U
Next, a classical player, maybe over rated in his particular genre but I don't listen to classical guitar much at all to tell. Paco De Lucia.
http://www.youtube.com/watch?v=RYkz30RL_GU
This next guy can go either way. Most people know who he is, but not sure if he is just popular on the underground or not. Buckethead. My favorite song of his is this one. Not sure if this is his best live performance or not as the sound on my computer is messed up so I can't hear it.
http://www.youtube.com/watch?v=_Et6BSDMNLY