A guy I work with put a 50CC scooter on Craig's list. My co-worker put in the ad that he only accepted CASH.
The only person interested was in a hurry and was willing to pay more than the listing. Of course they were a marine biologist on a ship in the Indian ocean and they would send a truck by to pick up the scooter. He would send a PayPal payment. It was for the guys dad.
My co-worker knew it was a scam instantly. His reply was "You are on a ship in the Indian ocean, cool. I am currently on the International Space station and we will be flying over the Indian ocean shortly. Where is your ship, I will take some picture of it for you." He had not yet received a reply.