Grave of the Fireflies has to be one of the saddest movies ever made in any genre
Pixar movies sneak up on me though. Cars gets me almost every time with the song "Our Town" about how the mother road faded away - my reaction always surprises me, but it is a wonderful song.
I've never heard that song before (or seen Cars) so I just played the song and felt something inside
It's a lovely song.