In no particular order

1. Reservoir Dogs (It's not Pulp Fiction but it is Tarantino... does that still count?)
2. Lucky Number Slevin
3. The Usual Suspects
4. Fight Club
5. Unforgiven (Clint Eastwood, Gene Hackman and Morgan Freeman... what more do you want?)

So glad no one mentioned "A Clockwork Orange"
I just didn't enjoy it like so many people that recommended it to me...

Honorable mention goes to
Will Smith in "Six Degrees of Separation"
T2: Judgement Day
Avatar (too predictable to make the top 5)