[Oni]

I would definitely second "Grave of the Fireflies". A good few years ago I selected it for one of the forum's anime viewings...

Did not expect it to be so heavy. Great anime, but also depressing as it follows orphans trying to survive WWII. Everyone left feeling more depressed and I realized I'd never pick another anime blindly after that. At the same time, I think everyone should watch it, since it is so unique. Studio Ghibli rarely misses.