One of my customers e-mailed his staff with a spoof e-mail purporting to come from Costa Coffee, which is the building next to his offices. All of his employees could claim a free cup of coffee and a Breakfast Bap on presentation of a voucher code; looflirpa 45688, he reckoned that he caught most of them.
Many years ago my wife started a new job in a bakery as a trainee manageress, her first customer that morning pointed towards some fresh cream cakes and said; "I'll have one of them and two of those" my wife wrapped them and put them in boxes. He then proceeded to choose nearly every cake in the shop which my wife dutifully boxed up until the pile of cakes was so high she could barely see over it. She was well made up and thought she was going to get a saleswoman of the year award. As she stacked the last cake the guy said "It's my Birthday next Thursday week, I'll be back then". He turned on his heels and walked out of the shop, all of her new colleagues rolled about laughing, apparently he was the local nutter and tried it on with every newbie on their first day.