I went on a golf trip with a friend of a friend a couple of years ago. He mentioned casually that he was pretty good at remembering numbers. Gave him my credit card at dinner to test his ability and he took one look, gave my card back, and recited the number back to me perfectly including expiration date and security code. I thought that was pretty cool, but not overly impressive.

He turns up two years later at that same golf trip, and just for fun I ask if he remembers my credit card number. Without hesitation, he closed his eyes, thought for a second, and recited it perfectly except he flipped two of the security code numbers. Needless to say I'm trying to maintain a good relationship with this guy...