I ran into a guy like that once whose story was that he needed to buy two tires for his car so that he could travel to wherever he was from to deal with some kind of emergency involving his parents. He claimed that he'd zeroed in on me in the supermarket parking lot because "you have a car just like mine."

It just so happened that I had recently had to replace the tires on my car, and two of the old ones were not completely worn out, so I had them in the back seat. So I gave them to him. He had to take them or blow his cover whether he really needed them or not, so either I actually saved the day or, well...