Doesn't necessarily mean the most Oscar worthy, just the one you most enjoy watching for whatever reason
Mine: Daniel Day-Lewis in Gangs of New York - lovely stuff - closely followed by Malcolm McDowell in A Clockwork Orange. <3 both those intelligent, charismatic sociopaths. And a third place podium finish for - and unless you've see the movie, this is going to sound embarrassing - Val Kilmer as Doc Holliday in Tombstone. Everything else he's done is stunningly poor, but he's schmick in that.