7. Leonardo DiCaprio Billy Costigan in The Departed
Billy Costigan is the son of a deceased criminal, whos immediately written off to have a career as a Boston State Trooper. His only chance to serve them is by being flung into his fathers old gang to infiltrate them and have his life constantly on the line - one hell of a role to play, and DiCaprio did it flawlessly. In all of his films he impresses me, but this role really stood out as the best of his career so far. Complimented nicely by Matt Damons confident and self-assured performance as Costigans opposite number infiltrating the Police, DiCaprio engages the audience brilliantly, making you really want Costigan to get out of this story alive.