Why this pick: Set in the frozen isolation of Antarctica, The Thing delivers one of the most terrifying monsters ever put on screen — a creature that can imitate any living being. What makes it truly scary isn’t just the monster itself, but the paranoia it creates. No one knows who’s human and who’s not, and trust completely breaks down. The practical effects are still legendary, and the atmosphere is pure tension from start to finish. Monster angle: A shape-shifting alien that becomes whatever it kills — meaning anyone could be the monster.