Riddle: You are surrounded by a Native American tribe who want to kill you, they say "You can say one true or false statement, no questions. If it's true we'll hang you if it's false we'll shoot you!" What do you say?
Answer: You will shoot me. because if they will shoot you your statement would be true, but if they hang you then your statement would be false so they would have to shoot you, so it loops around in a circle and they can't hurt you!