The Dark Knight Rises
Fans went nuts over the ending scene in The Dark Knight Rises. In the scene, Albert seen Bruce in a crowded cafe after he had apparently died when he saved Gotham City from a nuclear bomb. Fans had to wonder: was this just a figment of Albert's imagination, or did Batman really die? It's subtle, but the film does show that Bruce does fix his autopilot and was able to exit the aircraft before the bomb went off.
Life of Pi
After the boy on the boat got rescued, he told his survival story to Yann Martel. The story he told was completely different than the story that the viewers saw. Yann asked the boy if it was real, and he only gave a vague answer. Viewers were left to question why the boy would lie, and the only real answer is that the boy was questioning his his own reality.