4. Aaron Tricks The Legal System - Primal Fear
The Ending: After defense lawyer Martin Vail (Richard Gere) spends the entire movie proving to the court that his murderous client Aaron Stampler (Edward Norton) has split personality disorder, justice appears to win out and Aaron is sent to a mental hospital for treatment. However, when Vail visits Aaron again, he reveals that he doesn't have a split personality, and the sweet-natured "Aaron" persona never existed: he was merely an act, whereas the real personality is the brutal, sadistic "Roy". For his act of murder, Roy will go to hospital and upon convincing the doctors that he's all better, will be released shortly thereafter. Vail leaves, completely shell-shocked, as Roy laughs.
How It Trolled Audiences: Our reaction is almost exactly like Vail's own: What. The. F***!? Though a movie likely wouldn't get away with this sort of ending now, two decades ago it felt fresh and original, and when the true nature of Roy's scheme was revealed, we couldn't believe we'd been fooled. That the bad guy gets away with it, that he's laughing while he does it, and that the good guy can do nothing to stop him all adds up to make this a supreme uber-troll of an ending.