Okay, so this one is SUPER hard. Good luck ;)
You wake up in a room with two doors and two computers. You know that one door leads to life, and the other leads to death. You also know that one computer lies, and one computer tells the truth, but you don't know which is which. These computers know all. To get out of the room safely, you must ask ONE computer ONE question (i.e. along the lines of, "which door lets me live?"). What question do you ask?