Top 10 Tragically Depressing Movies You Won't Want to Watch More Than Once

This is a list of films that nobody wants to watch twice based on their incredibly heartbreaking subject matter.
The items in this list have been selected by the author of the list for you to vote and comment on.

The Top Ten

1 Requiem for a Dream
2 Schindler's List
3 Grave of the Fireflies

I watched it twice... or thrice...? - Misfire

4 12 Years a Slave
5 Precious
6 Irreversible
7 Blue Valentine
8 Hotel Rwanda
9 Dancer in the Dark
10 Brokeback Mountain