This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Plan 9 from Outer Space
You wouldn't think this film would have any, but if you've seen the film Ed Wood, then the scene with Lugosi outside his house will likely be this for you. The narration about the old man leaving "never to return" just makes it worse. Lugosi's performance in the opening funeral scene is quite effective. It's also an occasion where Wood's limited budget improves the scene - the tiny number of extras at the funeral adds weight to just how much the old man has lost.
On a rather meta level, there's also the fact that this is the last film the once-great Bela Lugosi ever appeared in. Turns Heartwarming when you learn why he was in it: Lugosi's career had dried up after he'd become addicted to painkillers and he was languishing away in near-poverty, but Wood offered him roles in several of his movies to give Lugosi some much-needed income in his old age, even helping to pay for his treatment to kick the addiction.