5. Sleepaway Camp (1983)
Spoiler Alert! Angela turns out to be not only the killer, but a boy as well. Angela is actually Peter, Angela's brother. The real Angela died years earlier, and Peter assumed her identity after being dressed up in girl's clothing by their aunt. We realize that she is really a he during the film's climax, when he reveals himself in all his glory, naked beside the lake, holding the head of his final victim. Eat your heart out, Crying Game.
4. Psycho (1960)
Spoiler Alert! Norman, apparently a great mimic and voice-thrower, dressed as his mother to commit the murders. Years earlier, he killed his mother -- whose skeleton sits in his cellar in a rocking chair -- and developed a split personality: that of him and his mother. The movie's little-known alternate title was Freud's Field Day.
3. Saw (2004)
Spoiler Alert! The man who appears to be the mastermind behind the "game" is in fact a player himself. He's being forced to act by the true mastermind, the man posing as the dead body in the bathroom. Lawrence eventually cuts off his foot in order to escape (presumably bleeding to death), at which point the "dead body" rises and proclaims to Adam, "Game over," locking him in the room to die.
2. Night of the Living Dead (1968)
Spoiler Alert! Ben, the last person left alive in the house, manages to survive by locking himself in the basement after the zombies break in. The cavalry arrives the next morning in the form of a bunch of good ol' boys shootin' zombies real good. Unfortunately for Ben, as he runs upstairs to greet the rescuers, they mistake him for a zombie and put a bullet in his head. The hopelessness of the ending embodied the war-ravaged era and, combined with the (unintentional or intentional) racial implications of Ben's death, made for one powerful bummer.
1. The Sixth Sense (1999)
Spoiler Alert! Malcolm helps Cole learn to use his power for good. The end. Oh, and Malcolm is really a ghost who doesn't realize he's dead. When anyone mentions "twist ending," The Sixth Sense comes to mind, and for better or worse (probably worse), it's spawned a generation of films that feel they must "trick" the viewer into liking them. Pretty sneaky, sis.