Haha, some jokes I know are:
1. How are you? 怎么是你? How old are you? 怎么老是你?
2. One car come. One car go. Two car "peng peng". One car die. (the description of a traffic accident...)
3. You have seed, I give you some colour to see see!
Oh, and I remember another joke -- a sign in a Japanese hotel: "If the air conditioning is too hot or too cold, please control yourself." (控制你自己???)