Oh boy, after working in retail from the ages of 15 to 21, and in multiple shops, I have many a story to tell.
Oxfam: You'd get the typical asking for discounts! No, it's a charity shop, we're not going to discount stuff. And people stealing! We weren't allowed to stop them if it was just one person on the shop floor, in case they got violent. I saw one guy shoving video tapes down his jeans.
Tesco: Again, like a lot of people, getting those idiots who think they can get away buying alcohol, looking young and not needing ID. So many times they would complain, and moan about it. But it's the law! I'm not getting in trouble because you couldn't remember your id.
Waterstones: I did a Christmas temp job at Waterstones, and so many people were rude and grumpy. The stand out guy comes up to the till, where there is a long line of people and starts asking me to find a book on the system. That's no problem, but all the information he gives me is 'golf, its a little book, tiny book on golf, I can't remember anything else'. Obviously I need more information than this to find the book on the system, which I tell him politely so he starts yelling at me, saying I'm stupid and can't do my job. The manager comes over, takes the customer over to another till to sort it out. Felt a bit worried about it until said manager came over and said not to worry about it, that was customer was a ****.
And finally, the mother of all jobs, Build-a-Bear Workshop!
Most of the time it was great, kids were happy and parents were happy because their kids were. But the minute school holidays were out, things descended into hell. Especially at Christmas time. People would complain at how expensive it was, do the 'if you don't work at school you'll end up here' (I'm currently studying engineering at uni so shut up), and parents thinking we're a nursery and leaving their kids in the shop while they go look next door!
One time we had a girl throw a tantrum because she couldn't get what she wanted so she spat over a load of stock. Had to get rid of it all, it was disgusting. Also, don't give your kid and icecream or burger and then come into the shop! Scraping up trodden in burger is not pleasant.
Oh well, at least I'm out of retail now! Hopefully for good!