Good Riddles

Question: To many, I am life's source. I am also its most valuable resource. I create and burn my own precious element, and my destruction will be my punishment. What am I?

Question: Turn us on our backs and open up our stomachs You will be the wisest. What am I?

Question: I shoot people and sometimes cut off their heads. What am I?

Question: A man travels by wagon,
brings joy each evening,
but depression by the morning.

Who is he?

Question: How many tickles do you need to make an octopus laugh?