My favorite was right after 9/11 - I was on an Airtran flight from Williamsburg to DFW. The pilot comes on and says"Welcome to our flight. If you see anyone about to commit a terrorist act, please feel free to beat the crap out of them, tie them up, interrogate them and then beat the crap out of them some more. Anyone who helps will get two free round trips to practice beating the crap out of other terrorists at Guantanamo Bay. However, please remember that while they may look mean, the flight attendants are only considered terrorists in parts of Wyoming and southern Canada. They are not the terrorists we are worried about".
The flight attendant came on to give her spiel a few minutes later, and afterward said "Please remember what our captain said about terrorists. Captain Kangaroo will be taking off shortly. Hopefully this time he will remember to bring the plane with him".
I am still not sure what was going on between them, but it sounded interesting.