10. The Untouchables vs. Al Capone (The Untouchables)
Source: Warner Bros.
Adapted from the equally excellent Hong Kong movie Infernal Affairs, The Departed follows a Boston gang and the city's police as they go toe to toe, round for round, tortured accent for tortured accent.
Billy Costigan is a police officer undercover with the gang, secretly feeding information back to the police, while Colin Sullivan is a criminal working for the police and secretly feeding information back to the gang.
The two characters spend the first two thirds of the movie dancing around each other like featherweight boxers, each trying to find out the identity of the other while concealing their own covert role. And when the movie reaches its climax, things kick off in a violent – and excellent – culmination of betrayal and confused identity, with a showdown on a rooftop involving a criminal who everyone thinks is a cop and a cop who everyone thinks is a criminal. And that, incidentally, is how every movie should end.