Boondock Saints
This film was an instant cult classic. Quick overview, Two Irish lads were put in a position by the Russian mob to fight back. They ended up killing a couple and decided that it was up to them to rid the world of evil. So they started killing off mobsters left and right with the aid of a close friend and an FBI agent. Some great killings and a damn good film. 9/10, buy it, dont rent it.