Best to me would be Lucario. His high-risk, high-return ability can be destructive. :D
MY Top 10 (in order of how good I am with them):
1. Lucario
2. Luigi
3. Meta Knight
4. Kirby
5. Toon Link
6. Link
7. Pikachu
8. Ike
9. Sonic
10. Wario
Also, check out my Brawler Card in my sig. Help it level up if you want to. :D
Something funny: I just bought Brawl yesterday. :P (Before I bought it, I played it a total of 4 times. (in chronological order) 1. At Gamestop a few days after it was released in the US, 2. At a friend's house 3. Another one of my friends came to my house and brought his Wii (I didn't have one at the time) 4. same as #3 (I still didn't have one, but I did get one on Christmas)