1. Jennifer Connelly and Heather Litteer in Requiem for a Dream (2000)
Requiem for a Dream is a great movie to rent if you want to convince yourself to never touch drugs again. Any of them. Not even Advil. If watching the mother and son pair (Ellen Burstyn and Jared Leto) slowly disintegrate from the effects of amphetamines and heroin isn't enough, viewers also witness the complete destruction of his gorgeous girlfriend Marion, played by Jennifer Connelly. Smiling and fresh faced in the early scenes, she's the image of fear in the final shot.
In a desperate bid for dope at the end of the movie, Marion goes, erm, back-to-back with an unnamed "party girl" (Heather Litteer) on a stage surrounded by grimy men in suits clutching wads of money. Sex for money scenes can be hot, but only if the women look like they're actually enjoying the transaction. Marion's face shows only fear and hopelessness. Combine that with the weaving montage of the other characters, whose situations are as bad if not worse that Marion's, and this scene officially embodies whatever is the exact opposite of sexiness.