In Scorsese's gangster classic The Departed, DiCaprio plays Billy Costigan, a young member of a famous mob family from South Boston who decides to become a double agent, ratting out secrets to the Boston police. DiCaprio gets brownie points for the South Boston accent, and for emanating such a strong sense of panic-stricken paranoia that it'll make you shift in your seat as you watch. It takes not a little skill to outshine Hollywood co-stars Matt Damon and Jack Nicholson, but it's all in a day's work for Leo.