Inception
This is probably the only theory that makes sense about Inception. The whole movie is a flashback - Cobb's flashblack of the Saito extraction and the Fischer inception - which lead to Cobb entering limbo. The kicks waking up the dreamers destroyed Cobb's limbo - the city skyscrapers falling apart - and replaced it with Saito's limbo. It is assumed Cobb and Saito shot themselves to wake up from limbo.