A Clockwork Orange
Just to give you an idea on this one, under the title is says "Rape,Ultraviolence,and Beethoven" It's one trippy movie. With a good mixture of violence, comedy, and music. Believe it or not, I first saw this in my Film as Literature class.

Pink Floyde the Wall
Good music along with a proper dose of insanity(also works extremely well with hallucinagens).

Any and all Cheech and Chong movies
They're hilarious and can make you drool from time to time(ie. the weed truck).

Fear and Loathing in Las Vegas
It's based on a true story about a reporter and a lawyer who go on a very long drug binge. I've never seen so many drugs in one movie in my life.

Bong Water
A good comedy.

Half Baked
Although it's a little unrealistic, it's pretty funny.