Anything to do with bodily fluids. Watersports and the like are right out the window for me. I don't like blood play of any kind either, especially if it involves knives because somehow it's worse when there's a clean, thin cut involved. And I don't like sperm or female juices or whatever. Mentioning them in appropriate parts of the sex scene is totally fine, but once they become the kink and the focus of the scene, it starts to squick me.

And my number one squick in fanart is when two characters have kissed and there's a thread of spit hanging between their mouths. Damn, do I hate that.