I'd say Gurren Lagann. I mean, it doesn't evoke the same amount of raw emotion as Grave of the Fireflies (because I don't think anything does), but . . . well. You've just gotten past the final fight, and everyone's celebrating, and . . . then that wedding, and the closing part of the framing scene. It's like a punch in the gut, and it absolutely makes sense in the context of the story. That was not easy to pull off.