Pascal's Mugging is a problem in Decision Theory involving extremely tiny probabilities of stupendously huge rewards.
It was originally described in Pascal's Mugging: Tiny Probabilities of Vast Utilities:
Suppose someone comes to me and says, "Give me five dollars, or I'll use my magic powers from outside the Matrix to run a Turing machine that simulates and kills 3^^^^3 people.
Most people intuitively think the correct answer is not to pay, but it is difficult to come up with a formal decision algorithm which refuses to pay but does not behave in intuitively stupid ways in other circumstances, such as continuing not to pay even if the mugger provided compelling evidence of actual matrix lord powers....