Riddle: you may only speak a single statment, not a question.
if it is true, raise your right hand,
if it is a lie, raise your left hand.
your statment must combine truth and lies.
Answer: "I will raise my left hand"
when you raise your hand, you'll make it true, so you raise you're right hand, thus making it false, so you raise your left hand, thus making it true.
and so on and so forth, you just made truth and lies become one.