I worked for Mervyn's for the Christmas season back in high school. Had a customer get mad because I laughed when he asked another associate if he could buy the display sheet/comforter set because it was the last one. Hell, I was 17 and had never heard of doing that. Had one of the managers get mad because I was wearing slacks that were the same color as blue jeans. She called me on a dress code violation (we could not wear jeans), and I called her on her nearsightedness. Had a customer yell at me when their credit card was declined, like it's my fault they cannot manage their card balances.
When I worked for Autozone, we had a woman come in to return some parts. I don't recall the exact amount, but it was somewhere around $500. I got the assistant manager's ok to do the refund, as she had a receipt from a different autozone. As she is walking out the door with her refund, the manager comes out from the back to stop her. Turns out that he had just been on the phone with the manager from the Autozone that she had bought the parts from. She had used a rubber check, and had pulled the same scam before. Anyway, the manager ran out, telling her that her check bounced and that the parts were considered stolen. He took pics of her car and came back in and called the cops.
The dipshits that came in with their home-grown dirt track race cars were the worst. "I need a fuel pump for my '73 Maverick, it has a V-8." After I look it up and get the part, they tell me that it's not the right part because they have a "Chevy 350 in there". Really, fucktard, you could have mentioned that at the start of this little transaction!
Or they would send their wives/girlfriends in with a parts list, then we'd get a call 45 minutes later because Princess came home with the "wrong part". Or the guys that thought Autozone is a full-service garage and want us to diagnose all their little auto problems.
When I worked at Pizza Hut, we'd get the people who would eat the entire pizza, save one slice, then ask for their money back because that one slice had a hair on it. One lady would call in once a week, order the same thing for pickup (at the time we did not deliver), then call half an hour later to complain about the pizza. After a few weeks of this, the manager finally told her that she was not getting any more free pizza unless she brought the old one in so we could see what the issue was. Another woman would come in and order a medium pan supreme and a diet coke...and then eat the whole pizza by herself in one sitting. On Sunday, all the church people would come in for lunch after the service and not tip because the waitresses were working on the Sabbath.