The Howling: Bill gets bitten by a werewolf and sex-starved Marsha offers herself to him. They have mad, sweaty, howly sex, and she even licks his werewolf bite, which seems like a really bad idea. Soon afterwards, he starts drooling. Lots and lots of drool. During sex. And then he turns into a wolf, and so does she. Which is good, because otherwise she'd probably be pretty grossed out by all his sex-drool.
Dagon: A poor innocent woman, who's just in the wrong place at the wrong time, gets offered up to Cthulhu in this Stuart Gordon masterpiece. "We will live for eternity," the priestess says, "and so will your child."
Possession: The psychotic Anna creates a lizard creature (with tentacles) out of her monstrous id, and at one point her husband Mark walks in on her having sex with the creature, in the missionary position. "Almost," she breathes over and over again, "Almost." Until Mark finally walks out.
Species 2: Two monsters have sex in this bizarre awesome clip from Species 2, featuring the notorious "nipple tentacles" that come out of Sil's breasts.
The Entity: And then there's this weird scene where a ghost rapes Candace... It's brutal and awful, except that some special effects wizard had to spend hours figuring out how to make her breasts look as though an invisible entity was squeezing them. It actually looks quite silly and undermines the otherwise chilling and horrifying scene.
Breeders: An alien monster controls the minds of tons of female virgins, compelling them to come to its sewer lair, where they cover themselves with its nasty alien sperm. Because. Imagine how uncomfortable this scene must have been to film.
The Hills Have Eyes 2: This mutant has an incredibly long prehensile tongue... but then the heroine bites it off and kicks him in the crotch.
Galaxy Of Terror: Another hideously disturbing clip, not for the faint of heart. The most famous worm-sex scene of all time, one which has spawned a whole new subculture online. Seriously messed up — if you didn't have a phobia of maggots, you will now.
Abducted By Daleks: And then wayyyy over on the campy side of the equation, there's this underground gem, in which the Daleks capture three women and enlist the aid of a dominatrix to try and tame them. But not even the Daleks' sex lasers seem to subdue their beautiful captives...
Evil Dead: Sam Raimi is a sick fuck. How else do you explain this scene where a tree tears a woman's clothes off and tries to have its way with her? Like a lot of these clips, it straddles the awful line between campy and unthinkably awful. Definitely not something you should watch if you're easily triggered, although it's on Youtube, weirdly enough.