Inception

[Ouch!]

EDIT: Except there is ONE thing that completely discredits this theory (SPOILER)and that is the fact that in every dream sequence Cobb is wearing his wedding ring. In every reality sequence he is not. In the final scene the ring can be seen.

Are you sure about this? Because other people are saying that he is definitely NOT wearing his ring during the final scenes. And if the ring serves as the audience's totem, then it means the ending was (SPOILER)reality.

I just got back from seeing the movie a second time. I was specifically looking for this, but after (SPOILER)they wake up in the airplane, the camera never shows Cobb's left hand. The people in the airport were not looking at Cobb.

I also noticed the second time through that there is one point at which everything beyond could be a dream. When Cobb and Eames visit the chemist and he shows them the ten men sharing the dream in the basement, Cobb tests the sedative compound. When he wakes up from the memory of committing suicide in limbo, he runs into the bathroom to splash his face with water. Before he can spin his totem, he is interrupted by Seito. From this point forward, he never spins the totem again until the very end. It's possible that he hasn't actually woken up from the dream in the basement in Mombosa, but I still doubt it.