What's the funniest dirty joke you know?

I’m asking for a good reason. My uncle is sick with cancer and is going through some extremely difficult chemotherapy. I’ve been sending him a dirty joke each day to get him “through the next two minutes.”

I have now used up all my good dirty jokes. He’s an intelligent, thoughtful, kind-hearted, and dirty old man, so I really need some good stuff for him. To give you a sense of what I’m looking for, his favorite joke so far was when I sent him a transcript of Marty Funkhouser’s joke from Curb Your Enthusiasm.

Here it is in case you missed it: http://www.youtube.com/watch?v=3o5m_mXadoU

Thank you!