Gummo. Don't watch it, unless you want your soul shattered completely.
Oh, and Koyaanisqatsi. Its supposed to be this big, deep film about how we're fucking the planet, but...its just a montage of random fucking clips with irritating fucking music on a god damned loop for an hour. Fuckin Stu said it made him ashamed to be human, it made me ashamed I didn't just sleep thru the fucker when we watched it in Creative Writing class.