1. Usual Suspects
    Y'know, the whole Kaizer Soze (sp?) thing ;)
  2. Fight Club
    Yup a nice little twist near the end..
  3. Sixth Sense
    The late revelation from the freaky wee boy and the character played by the despicable Bruce Willis
  4. Memento
    I add this only because I witnessed someone ruin it - midviewing - for a friend. Spoiler alert pls.
    Suggested by @ameliaville
  5. Ex Machina
    Suggested by @kate81
  6. Any movie with Sean Bean in it
    Because most of the characters he plays die.
    Suggested by @betsybasom
  7. Seven
    Suggested by @kiraandlulu