"People who like this sort of thing will find this the sort of thing they like." (Lincoln)
Prisoner's dilemma
You stonewall
Both get 1/2 year
You get 10 years, he walks
You talk
He gets 10 years, you walk
Both get 5 years
Wikipedia has an entry on prisoner's dilemma, as does the Stanford Encyclopedia of Philosophy. And you can play the game on line.