9. Will The Real Jigsaw Please Stand Up? - Saw
Say what you will about the Saw franchise, but the original movie still boasts one of the most ingeniously unexpected plot twists - and villain reveals - of the last 20 years.
The film's central mystery pertains to the identity of Jigsaw, the serial killer whose M.O. involves putting his victims through perverse traps in order to test their will to survive.
Near the end of the movie, the big reveal appears to be that Jigsaw is Zep Hindle (Michael Emerson), a disgruntled orderly working at Dr. Gordon's (Cary Elwes) hospital.
Except, once Adam (Leigh Whannell) beats Zep to death, he discovers a cassette tape on his person, confirming that he was just another of Jigsaw's test subjects.
The iconic final montage then drops an all-timer jaw-dropper bombshell, as the dead body in the middle of the grotty bathroom stands up to reveal he was alive all along - Jigsaw has secretly been observing Adam and Gordon's game from mere feet away the entire time.
As it turns out, Jigsaw is John Kramer (Tobin Bell), one of Gordon's terminally cancer-ridden patients who wanted to teach the value of life to those who did not appear to appreciate it.
As much as the endless slew of sequels have tried to one-up the original's reveal, not one of them has ever gotten anywhere close.