I nominate Isao Takahata's "Grave of the Fireflies" It's a great movie, but if you are going to watch, I highly recommend that you don't watch it alone and tha

I nominate Isao Takahata's "Grave of the Fireflies" It's a great movie, but if you are going to watch, I highly recommend that you don't watch it alone and that you have something "fun" planned afterwords - maybe a fun dumb movie like The Hangover, play with your dog in the park, etc. Do not watch it by yourself and then go to bed. It is really haunting.