As Seen In: Sleepaway Camp (1983)
Oh, the toilet—there's arguably no place on which a person can be any more vulnerable. Seated and ready to handle your business, so to speak, a person's short-lived (ideally, anyhow) stay inside a bathroom is one of pants-down defenselessness. There's no better place for a horror movie's killer to attack his or her victims, which is something that the antagonist in Sleepaway Camp surely realizes.
The killer is also very creative. So, when it's time to get rid of one male character in the film, the killer waits for the guy to position himself on the crapper, sticks a broom through the outer handle to lock it tight, and drops an agitated beehive into the stall. Going number two has never been so grotesque.