From jennshrew, Tales From Retail:
Years ago I was an assistant manager for a children's clothing store. If you can survive there, you can survive anywhere in retail. There was a regular who would come in and most associates would avoid her because her visits usually consisted of rummaging in the stockroom for items, pulling out arm loads of product and she'd pick through it for over an hour before finally settling on a few cheap pieces. It was known that my store had all the best, cheapest clearance of the other locations in town. Since we were so heavy on clearance a lot stayed in the back since we didn't have room on the floor.
This went on for months were she would do this and I'd be the only one who would help her. One day she came in and I was working alone. Policy is that on single coverage we were not supposed to go to the stock room for checks. We either had to 1. Have them leave the store, lock the doors and then perform the stock check or 2. Write down their request, name, number, etc and call them when we have double coverage.
Since it was a relatively slow day I decided I'd make a quick few trips to appease her. Nothing I was bringing out she cared for. She then asked if she could go to the back and check. That's a typical "no" no matter where you go but I decided I'd let her. She was maybe back there a half hour and I kept poking my head in to see if she was ok. She came out with tons of stuff and bought several hundred dollars. I rang her up, sent her on her way and didn't think much of it.
She came in a week later saying she was moving her pediatric practice to the other side of the country and that's why she needed a new wardrobe for her kids. She thanked me for all my help and gave me a card. It was the sweetest thing. I opened it after she left and a $50 bill popped out. Now it was also policy that if we received tips we were to put them in the register and include it in the deposit. My store manager saw it fall out and told me to put it in my pocket right away instead. Needless to say I was blown away.
Those one in a million interactions make up for a lot of crappy ones.