Grave of the Fireflies
That one is rather depressing. I much prefer The cat returns and Spirited Away
I did one of my university theses on Grave of the Fireflies.
True fact: it was presented a double feature in theaters in Japan with Grave of the Fireflies first, and then My Neighbor Totoro second, on account of the fact Ghibli Studio was sure nobody would go see it on account of the fact it
is super depressing. So they paired it with the feel-good movie Totoro.