An Enlightening Riddle
Q. I weigh nothing, but you can still see me. If you put me in a bucket, I make the bucket lighter. What am I?
A. A hole!
Q. A prisoner is forced to go into one of three rooms, but he can choose which room. The first room is ablaze with fire. The second one is rigged with explosives that will go off as soon as he enters. The third contains a pair of lions who haven't eaten in years. Which room should he choose to survive?
A. The third room—any lions who hadn't eaten in years would be dead!
Source: Twenty Two Words