Be warned: No movie is safe in this thread, not even movies that are now in theaters.
In this thread, we spoil the endings or plot points for any and every movie you can think of. Here, you can spoil any movie you feel like spoiling, or if you don't feel like sitting through a particular movie, you can request spoilers. Remember, this is the only warning you're going to get. If you don't want a movie spoiled for you, turn away now.
Fight Club: The nameless narrator, Edward Norton's character, suffers from a split personality disorder, and Tyler Durden is the unleashed id of the narrator. He created Durden when he first saw Marla Singer because he immediately fell in love with her and didn't know how to communicate his feelings. It's explained much better in the book than in the film, but that's the key element that causes his life to snowball out of control. A lot of things in the film are in different order than in the book, but the biggest difference is the ending. In the movie, the buildings crumble taking the narrator with them (it's implied). In the book, the narrator's "friends" from the support groups come to talk him out of destroying himself along with the buildings.