I suppose when you say fav. you mean because the actor/actress was THAT good... right?
If so here it is...

1. Jim Caviziel - Christ
2. Jack Nicholson - RP McMurphy (1 flew over the cukoos nest)
3. Keanu Reeves - Johnny Utah (Point Break)
4. Heath Ledger - Joker
5. Ryan Phillipe - Sebastian (Cruel Intentions)
6. Al Pacino - Tony Montana (Scarface)
7. Jim Carrey - Loyd Christmas (Dumb & Dumber)
8. Denzel Washington - Alonzo (Training Day)
9. Gael G. Bernal - Octavio (Amores Perros)
10. Ed Norton - Derek Vinyard (American History X)