8. Casino Royale (2006)
The "False" Ending... Having defeated Le Chiffre, banker to the world's terrorists, in a poker game, James Bond's new found love interest Vesper is captured by the frustrated villain, and Bond pursues. He crashes his car on route, and is tortured by Le Chiffre for information, though is rescued in the nick of time by a mysterious character. Bond awakens in recovery, where he and Vesper - mission completed - vow to spend the rest of their lives together.
But Wait... With the bad guy dead and the happy couple reunited, you wouldn't expect there to be a further half hour to this movie, would you? And yet there totally is, because Bond soon discovers that Vesper has not been honest with with him for the entirety of their relationship, and actually agreed to exchange the winning poker money to Le Chiffre's organisation in exchange for her actual boyfriend's life. Bond investigates this, heartbroken, and Vesper is eventually killed when - haunted by her betrayal - she refuses to let Bond save her life after a huge action set-piece that sees the poor women trapped in an underwater elevator. This part may appear to drag somewhat, but that's presumably because the movie did such a good job of making you feel like it was about to end 30 minutes before it all happened. It's necessary story, nonetheless.