I'm not entirely sure. There aren't a ton of fantastic female characters. Mystique is pretty awesome, but I'd want to be able to fly. Can she fly if she takes the form of a character who can? Like Angel, for instance? Anyone know the rules on that?
I would definitely have to say Deadpool. Super ninja skills, regenerating powers, and because he is the only comic book character to consistently break the fourth wall. The split personality might be weird, though.
