Answer:
What is it that no man ever saw, which never was, but always will be?
Can you think of a crime that is punishable if attempted but not punishable if actually committed?
A man goes out in heavy rain with nothing to protect him from it. His hair doesn't get wet. How does he do that?
Spies and detectives do this to phones and musical shoes make this sound.
You are on an electric train. Which direction will the smoke fly in?
It is something you will never see again.