I guess my Lebanese/Cajun *** will rep the Asians?
Choi Min-sik as Oh Dae-su in Old Boy. If you feel yourself needing an explanation, watch the damn movie.
Eihi Shiina as Asami Yamazaki in Audition. Won't ruin the twist, but she completely sold it.
Tadanobu Asano as Kakihara in Ichi the Killer. He made this movie for me.
I know it might be viewed as lame, but I really enjoyed Jamie Foxx as Ray Charles....even though he hasn't dropped the act since.
Really can't argue with any of the names already mentioned, so I won't go and repeat them.
Denzel Washington as John Creasy in Man on Fire (That movie has a special place in my heart).
Samuel L. Jackson as Elijah Price in Unbreakable.
Ron Perlman as Hellboy. If you have even LOOKED at the comic you could see that Ron was a perfect choice to play HB. It's almost eerie, actually.
The very best though? Ledger in TDK for me. Unfortunately for us, it was a once in a lifetime performance.