1. The Departed - Billy Costigan
In his third teaming with Scorsese, DiCaprio lays it all out in the crackling mob thriller The Departed. Playing Billy Costigan, a Gung-Ho state trooper from the streets of Boston who goes deep undercover to infiltrate the Irish mob, DiCaprio gives a fearless and richly complex performance worthy of some of the greatest given under Scorsese's eye. In the film, Costigan immerses himself into the life of a petty criminal and transforms into a man that he can barely trust himself, let alone his cohorts. DiCaprio holds nothing back in letting paranoia and inner conflict take over in his character and he constantly has to play the role looking at his surroundings from both sides of the fence, and decide what side he should be pledging his allegiance to. Torment, remorse and fear in a character have never been displayed so well in this type of a film, and DiCaprio paints with many different brushes here. Mastering numerous scenes with the electric Jack Nicholson as the mob boss, makes this all the more a one of a kind performance. The Departed walked away with the 2006 Oscar for Best Picture (among others) although DiCaprio's work here was vastly overlooked (he did however receive his 2nd Best Actor nomination for Blood Diamond that same year).