OK, here's another one:
3 men split a pizza at an expensive Italian restaurant. Each man paid $10. The waiter took the money but was a bit pissed that he got no tip. However, when he delivered it to the manager the manager said that the pizza should only have been $25, and gave him five one-dollar bills to return to the customers. Since the waiter could not divide five dollar bills evenly by three, he decided to keep $2 as a tip and give each man $1 back.
Now, here's the tricky part: Each man actually paid $9 for the pizza. There were three men, 3x9=27, so the pizza really cost $27. The waiter kept $2. 27+2=29. So if there was $29 involved, where did the extra dollar go?