Grave of the Fireflies http://www.imdb.com/title/tt0095327/
I could not smile for days after watching that one. One of the greatest movies ever made, but when I recommend it to anyone, I always warn them that if they are depression prone, they should not watch it at all.
So _intense_. Even years later, just reference to it gives me goosebumps.
Yes. That's one of the best movies that I've only seen once. It occupies a rare intersection between shows that I consider excellent and shows that I'd rather not watch again.
I saw that recently, expecting something very sad, based on what people told me.
I wasn't all that upset with it though. The deaths weren't that traumatic..
[1] http://www.imdb.com/title/tt0914798/