My very first job was when I was 16. I was hired as a boxboy/'janitor' at my local Trader Joes. Basically, I kept the store clean, picked up trash, and was given the beer/soda/dairy products cooler to stock.
My worst moment was on a Friday afternoon. We were getting a shipment in. The driver would leave all of the pallets near the front door, and I would wheel them into the back with the hand truck. I went to pick up a 'flat' of eggs, which was crates of dozens of them stacked about 5 feet high. I didn't quite get the COG centered on the hand cart, and as a result, I dropped about 100 dozen eggs on the floor in full view of the customers. Talk about feeling 2 feet tall. Although I got a bit of a tongue lashing in the back, no further disciplinary action was taken; my boss felt that being embarrassed like that and being laughed at by the co-workers and customers was punishment enough.
My best moment involved beer. Part of my duties was to keep all of the different varities of 6 pack bottles stocked in the case. One particular brand, Asahi, we only got one case of, and it always sold out within hours. There was this one guy who would come in every Thursday looking to buy a 6 pack of it. Of course, by the time he came in, it was always sold out. And he was really bummed about it. He wouldn't buy any other brand. He was always after that Asahi. So on the next shipment, I immediately intercepted two six packs, and hid them in the cooler, where the public wouldn't be able to see, much less buy them. Sure enough, he came in. And when I went around back and got the two that I set aside for him, he was so happy that he went to my boss and ranted and raved and gloated about my 'service'.
I guess my boss was so happy that he gave me a free paid day off as a reward. Mind you, a typical day for me was only about 5 or 6 hours. So it wasn't a lot of money. But I was still thrilled.