Two movies that I thought were absolutely amazing, but may never watch again: Grave of Fireflies and Black Swan.

The emotional gut punch of both of them can't be overstated. If you haven't seen either, you need to, but one watch is enough. They are horrible and beautiful and hurt you so goddamn much, in two very different ways.

Honorable mentions are Requiem for a Dream and American History X, for similar reasons.