Terminator 2 - Judgement Day IMO. A machine in the future sent back in the time to kill a teenager named John Conner which in the future will save the world.
Pulp Fiction. Not a movie better. Three story lines about a professional boxer, 2 hitmen, and a night out. Great movie, must watch if you already haven't seen it.
The Usual Suspects - A tale of a group of criminals working for the world most notorious and faceless villain, Keyser Soze.