Also not a movie... But Robot Chicken is pretty classic ... One show that can take the piss outta anyone in a skit less than 30 seconds long at times!
And then there's the main list:
Fear & Loathing in Las Vegas
Pulp Fiction
Donnie Darko (Although if you've never seen it, it's a bit like; wtf is going on? - Specially when your ultra high lol)
Requiem for a Dream (a good movie, but be warned, it's also very depressing)
Super High Me
Pineapple Express
Step Brothers
Aqua Teen Hunger Force Movie
Trailer Park Boys Movie
And many more I believe! lol