Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Angel's Egg
The scene when the man and the little girl are talking in the girl's "house" and he says something along the lines of "maybe we aren't real, maybe we're all just a memory of someone else, and it's raining outside".
It's easier to name the parts that aren't soul-crushingly sad... The dead, empty world where everything and everyone has forgotten their purpose, the little girl's death after the man she just got attached to shatters her egg/symbol of hope, when she dies just before she can reach him, the grim, alternate Noah's Ark story where the olive leaf never came, and last but not least, the half-sunken Ark itself amidst the black, endless sea...