The house not answering the door
I mean, Jamie Lee Curtis' character is absolutely terrified and yelling for help, yet the people in that house she goes to will go so far as to turn on the porch light, but they turn it off again almost immediately as they reject her pleas for help. That smacks of a contrivance that I just can't buy, they must've been heartless bastards for ignoring her like that. And if that is a typical staple of slasher movies, then IT SUCKS.