Rec advent calendar prompts?

Last year as a present to my roommate I made her an advent calendar of fic recs: she gave me a list of 24 of her favorite tropes and every morning she got a fic rec for one of them. It was a lot of fun, so I decided to do something like that again. This time I decided to ask you guys: tell me a favorite trope of yours and I'll look for a story to rec you in December :)

A few caveats: The order will be random. Restricting fandoms would make it more difficult to find stories that fit, so while I will try to find a story in a fandom that I think you're familiar with, it's not a guarantee (else I'll look for a story that doesn't require canon knowledge or an original fic.) Tell me your DNWs so I can avoid them.