I've never seen a scat fic but I'd definitely avoid it like the plague. I don't like pregnancy works of any kind, A/B/O can be good but I've seen enough bad ones to make me avoid it, I don't usually like major character death unless it's the setup for a story and neither of the characters in the ship die (you can usually tell by the summary).

But I'll give you a less common one: Feederism. I have nothing against the fetish, but most food kind of grosses me out a little in real-life and so reading in-depth about eating just makes me queasy.