Kirby Is the best all around. Ike can be amazing if you'can dodge and are smart with him. Sonic is great as a fast, and somewhat cheap character. But Pikachu is more deadly than all of them if you're experienced with him. I'v seen three pretty good people lose to one Pikachu.
I can beat ANYTHING with Toon Link. Fast, powerful, great to recover, and can do a secret combo in the air that I figured out that'll do like 200 damage%!