A British game-show called "Golden Balls" concludes each installment with a single-shot version of the Prisoner's Dilemma in which the two players' choices can result in a large cash prize being awarded to both of them, neither of them, or just one of them. The players are allowed to tell each other what they plan on doing, but they are also allowed to lie and try to trick the other player into making a choice that would leave the whole pot in the trickster's hands.
In this remarkable clip, a player named Nick runs an extraordinary end-game that has to be seen to be believed. As Bruce Schneier says,
This is the weirdest, most surreal round of "Split or Steal" I have ever seen. The more I think about the psychology of it, the more interesting it is. I'll save my comments for the comments, because I want you to watch it before I say more. Really.
Once you've watched the clip, check out Bruce's spoiler-y discussion of what is going on there.