My two favorite characters are Bowser and Pichu.
Bowser: His smash moves are so powerful, and he's ultra hard to get off the edge if you play him right. He may be slow, but he makes up for it with his power. Like his up smash in the air, that's almost as powerful as Links down smash in the air...the cheap move *shakes fist at link's stupid move*
Pichu: Pichu seems like a weakling, but have you ever used his left/right b attack? The one where he charges up. I've killed Bowser, played by human, at 40% damage with that move at full charge. The little mouse's got spunk. 'Nuff said.
Curse you stumble button!