We all know and love (or hate) the various tropes that can be found within the Harry Potter fandom, but sometimes after a few good binge reads, these tropes can often get overused. I've recently been looking at, and surprisingly enjoying, some crossover fics, despite my initial misgiving. They put quite the refreshing air into the HP universe or refreshing character development of HP characters in another setting.

I was wondering what others think of crossover fics, what's your favorite combo, and what type of trope do you enjoy.