This thread seems unfair, yet I can't say I'm not in favour.
Yo Dexter: There are two men, one who tells the truth and the other always lies. You don't know which is which. There is a door to life and a door to death. You don't know which is which. What question do you ask one of the men so that you can go through the door to life if you don't know which man is which and which door is which?