I watched Grave of the Fireflies this evening. It was so freaking depressing! The same studio produced some of my other favorite animes like My Neighbor Totoro, Spirited Away, Kiki's Delivery Service, and Howl's Moving Castle. Those movies while containing some serious subjects like war, illness, and family dynamics, were fairly playful. This story takes place in Japan during the second world war. You can feel the pain, fear, and struggle throughout the movie. I forgot I was watching an anime. It was brillantly tragic. I layed in bed for a half hour afterwards.
Some professional critic comments pretty much sum up my feelings ... "Roger Ebert considers it to be one of the most powerful anti-war movies ever made. Animation historian Ernest Rister compares the film to Steven Spielberg's Schindler's List and says, "it is the most profoundly human animated film I've ever seen."
http://www.imdb.com/title/tt0095327/