I love twist endings. I love having my expectations for a film twisted in on themselves to reveal unseen truths about the characters and their previous actions. However, a twist ending is only good when the viewer is not expecting it.
Take for instance Frank Darabont's 1994 prison drama "The Shawshank Redemption". During its finale, the warden (and the viewer) discover that Andy (Tim Robbins) has not only escaped but that he had been digging a tunnel to get out for over twenty years, during which the film takes place. When I first saw the film, I had no idea that this would happen. Andy seemed very indifferent, spending his time reading books and making a chess set out of rocks from the prison courtyard. What he did and who he talked to seemed of no consequence. However, on repeat viewing I noticed how every word he said, everywhere he went, was to get himself closer to his goal: freedom. That's what is so wonderful about twists. They make viewing a movie for the second time even more enjoyable than the first.
Not all twist ending work out as planned. This is the case in "Wanted", a blood-laced and adrenaline-induced comic book adaptation with James McAvoy, Angelina Jolie and Morgan Freeman. Despite director Timur Bekmambetov's attempts to surprise the audience with McAvoy's sudden revalation that the man he was hired to kill is, this twist never took me. It seemed to me that in an already convulted plot, this twist seemed too routine to make an impact.