Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Tiny Toon Adventures
Anviliciousness aside, the mother whale being captured in Whale's Tales.
The whole third segment of Cat's Eye View: Homeward Bound. Just watching it brought me to tears.
Furrball and the ribbon.
The newsclip from Fields of Honey, particularly when Bosko fades away into oblivion.
Bosko:Honey...
Babs:(crying) That's the saddest thing I've ever heard.
This is even worse when you realize the same thing will happen to the Tiny Toons, due to them being forgotten over time. Someone actually did a fanfic of this... it was depressing.
Later, when Babs realizes that the old lady she encountered turns out to be Honey, who turns back into her old youthful self when everyone laughs at her cartoons again.
Then Bosko and Honey are reunited and dance off into the moonlight.