The worst I ever had was an old woman who was also clearly a hardcore tweaker. She came in, had me count the random fistful of coins and cash she had, and then kept bringing shit to the register and asking me if she had enough. This went on for a good forty five minutes. If she didn't have enough, she wouldn't just ask to buy some of the items. Rather, she would start her search all over again and bring up a completely different set of random shit. Eventually she brought some stuff that she could afford, but when we finished the transaction she spent another fifteen minutes telling me about how God has her back.