Answer:
What is as big as you are and yet does not weigh anything?
A claustrophobic person gets on a train. The train enters a tunnel just as it is leaving the station. Where is the best place for him to sit?
I have two coins, one is marked George I and one is marked George IV. One is genuine but one is a forgery. Which is the forgery?
What can you hold in your right hand but never in your left hand?
What goes up the hill and down the hill, And spite of all, yet stand still?
I only exist when you are here. Where you never were I can never be.