Can think of way too many good films to put them in any sort of order, but here's a few that might make my top20...
Delicatessen
Man Bites Dog
Jacobs Ladder
Full Metal Jacket
The Deer Hunter
Pulp Fiction ...and Reservoir Dogs (don't make me choose)
The Godfather (even part3)
Alien
Goodfellas (and Casino)
The Thing (or anything by John Carpenter)
Predator
Crouching Tiger, Hidden Dragon
Battle Royale
Fear and Loathing in Las Vegas
Up In Smoke

Trainspotting
Snatch
Deliverance
Texas Chainsaw Massacre
The Matrix
Enter the Dragon
The Shining
Scarface
28 Days Later (sequel's good as well)
Sin City
Dog Soldiers
Jaws
The Omen
Huo Yuan Jia (Fearless)
Monty Python and the Holy Grail
Natural Born Killers
Chopper
The Good, the Bad and the Ugly (and anything from Leone)
A Clockwork Orange
Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb
True Romance
Repo Man
Donnie Darko
Fight Club
The Italian Job (not the 'remake')
An American Werewolf in London
Apocalypse Now
Pitch Black
King of New York
The Shawshank Redemption
....OK, I'll stop there
