Requiem For A Dream. I've been having depressing thoughts ever since I watched it, and even though it's a really good movie I don't want to watch it ever again
Brokeback Mountain, it was the first gay film and still the most powerful I've seen. It just showed me how, as great as love can be, it could also ruin you. In a way that film made me terrified of falling in love, as I'd never want to wind up in that kinda life.
But then again it also made me grateful to live in a more accepting and diverse culture.
Mulholland Drive, Memento, Under the Skin, Her, Milk, American Beauty and like many have said Dancer In The Dark... people will either think its silly or profound. I thought it was extremely touching.