I don't think I can pick only one, so here's a list:
*Ass-to-mouth or ass-to-pussy. I love anal, ass-play, rimming but it ruins it for me as soon as the cock or toy goes from the ass to the mouth or pussy. It's not sanitary. It might not make sense that I'm into rimming, but as long as it's on the outside it's clean as far as I'm concerned.
*Milk enemas, or enemas in general. Gross.
*Trashy-looking people.
*Landing strips or any pubic hair styles that leave the vulva hairless but not the mons pubis. Either shave it all or leave it alone, a pussy shouldn't look like the bride of Frankenstein.
*Condoms. I know it's a safety thing and I don't fault actors for wearing them, but it ruins it for me.
Ruining a perfectly good pussy or ass-fucking by pulling out and cumming on the girl's face. If you aren't going to cum inside, at least do it on her belly or ass. I don't have a problem with facials, sometimes it's hot if it's a good blowjob/handjob video, but seriously it's like *every fucking video ends with a load on a girl's uncomfortable-looking face.
*Fake moaning, shitty acting, etc.
*Lesbian porn where the girls have long nails and clearly have no idea how to eat pussy or get another girl off for real.
*Lolipops and other food products in the vagina. Enjoy your yeast infection.
*Pee porn where the girls piss into a glass or bowl before drinking it or pouring it on themselves/someone else. Or when they are just on the toilet. For some reason that really bothers me. I like watching girls piss into each other's (or their own) mouths, or onto each other, or onto themselves, but something about peeing into a container is just gross to me. Toilet peeing is too mundane, nothing sexy about it.
*That weird close-up shot of the girl's ass in skimpy shorts or a bathing suit or thong as she's walking or going up stairs. I like a nice thick ass, but there's something absurd about that shot/angle.
*Guys getting their asses licked or toyed. I'm not 100% straight, so I don't mind guys in my porn, and occasionally watch gay porn, but something about guy's assholes getting poked with fingers/toys or getting rimmed by another guy or a girl is just not appealing at all. I like all that stuff when it's a girl's asshole, and I like it when it's a dick going into the guys ass, but anything else, nothx.
*Bi porn that ends with the guys both cumming on the girl's face/chest. Keep it bi all the way to the end, guys.
*Excessive makeup and especially running mascara. Not attractive in the least.
*Girls saying they're 18. I don't care if she's actually 18, but as soon as the camera man asks "and how old are you?" she's instantly 25 in my mind no matter what she says. Not that I have a problem with older girls in porn, it's just the bullshitting that gets me really.
*When it's obviously cold in the room. I can see the goosebumps on the girl's pussy and the guy's shriveled nutsack. Crank the heat up for fuck's sake.
*When there's any delay at all between when the cum leaves the dick and when it gets swallowed. No, I don't want to see the puddle of jizz in your mouth. I don't want to see you sharing it with the other girl, I don't want to see you licking it off anyone's chest. Get it while it's hot, or it's just gross to me.
*Chubby or fat guys. My tolerance for body fat is a lot higher in women (as long as there's no rolls or fat-dimples), but if the guy has even a small beer gut or a saggy ass, it's a turn-off.
When the girl is trying *way too hard to look like jailbait. I'm talking schoolgirl outfits, neon-coloured headbands/hair elastics/etc, pigtails, really bubbly-sounding.
Jesus why do I even watch porn