A highly superior being from another part of the galaxy presents you with two boxes, one open and one closed. In the open box there is a thousand-pounds. In the closed box there is either one million pounds or there is nothing. You are to choose between taking both boxes or taking the closed box only. But there's a catch.
The being claims that he is able to predict what any human being will decide to do. If he predicted you would take only the closed box, then he placed a million pounds in it. But if he predicted you would take both boxes, he left the closed box empty. Furthermore, he has run this experiment with 999 people before, and has been right every time.
*What do you do? *
I've only ever heard of one satisfying response.