I love jokes and it would be pretty hard to come up with just one favorite. Usually they involve funny voices, hand gestures and impersonations, so don't necessarily translate well written down. I remembered one from high school that I thought was pretty funny so I'll tell you that one.
A fighter pilot is flying over enemy lines when he is shot down and captured. He is badly injured and his captors are forced to amputate his leg.
He begs them, "Please! When you are flying over my home country during one of your raids, would you toss my leg out, so that a piece of me might rest at home?"
They agree to do this and when they next flew over his country they returned his leg. Later he had to have his other leg removed and he asked the same question of them. They agreed once again and returned his other leg to his home county. Yet again, the doctors discovered they had to amputate his arm! He asked them if they could do the same for his arm as his legs. This time they refused.
"Why not?" the pilot asked? "You have done this many times before!"
The commanding officer turned to him and replied, "We think you're trying to escape!"
And we all roll on the ground laughing! Well maybe not, but it could have been a lot worse!