Obviously the illegal shit isn't going to fly with me. Beastiality, people being underage, necrophilia, snuff... then there are some things that would either gross me out/that I wouldn't be able to stop laughing about.. that would be impossible for me to find sexy. I don't think I could participate in a partner wanting to hump a stuffed animal. Also, there would be hell to pay if I saw them humping any of MY stuffed animals. Coprophilia, roman showers, farting, etc. Nope, nope, nope. Race play? Not going to happen. I already find it irritating when there are people whose primary attraction to me is my ethnic background.
Beyond that? Pretty damn open. Piss, blood, furry/anthro, hentai, etc. Doesn't bother me. Rape play? Sure. If I trust you enough. Choking? Same thing. Both play off fears/bad past experiences, but I'd be open to trying them if I really trusted a person.