Before Ebay had buyer protection I bought the first Panzer Dragoon game from a seller who described the item in very good, complete condition, but no pic was supplied. The price was good so I took a chance on it. Low and behold it was not complete when it arrived; the case and disc were original, but the manual/cover was a printed out one from a cheap black and white printer. I called the buy out on it, and of course he never responded. I then opened a case against him, but he literally abandoned his account instead of giving me a refund, which was interesting since I remember he had at least 40 feedback. Unfortunately I didn't get my money back for that one.
Another ebay horror story involved my girlfriend who bought something off ebay that arrived in a crushed Poptart box. Obviously she was pretty pissed about it and left negative feedback for the seller. The seller then proceeded to flip out on her and began sending her threatening messages. She reported the buyer and the buyer and his 4000+ feedback account were banned. This pissed him off and he proceeded to create fake accounts and harass her for the next month. She eventually got tired of dealing with it and because she knew the guy's name and address from the item she bought from him, she threatened legal action if he sent her one more threatening message. They stopped immediately after that.
This last one is more funny than bad, but I used to have a honey hole from about 2011 to 2013 where I found a ton of amazing deals on games. It was a 2nd hand media store owned by the now defunct Hastings, and before retro gaming/collecting became very popular it was a constant goldmine of new, amazing stuff coming in. Just as reference to how amazing it was, all retro games, which was everything before PS3/360/Wii was priced at $3 each regardless of title. I found games like Haunting Grounds, Skies of Arcadia, Conker's Bad Fur Day, Saturn Bomberman and so, so, soooo many other expensive items for just $3. Hell, probably 80% of my PS2 collection came from that place. But anyhow, around 2013 when video game collecting really started gaining traction, there was a guy that worked there who was a total scummy dickbag who would follow me around and see what games I would pick up and would love to ask me how rare/valuable they were. At first I thought he was just curious, but then realized he was trying to gain knowledge on what to snipe before it hit the floor. And snipe he did! At one point in 2014 he'd post several new ads on CL a day of stuff he picked up from there, and of course during this same time almost nothing good made it to the floor. I had to get clever to beat this guy, and I did this by gaining a good relationship with a few employees who would always check the back when I asked them about new retro stuff that came in. Because of this I was able to undercut that one employee, however by that time there were probably 4 other employees that were sniping the games too. Eventually my friendly employees either quit or were pressured to stop helping me, but that didn't stop me from asking employees who were either new or were at least somewhat decent. At one point there was this really goofy looking employee that really, really hated me for trying to purchase games that he felt entitled to. One evening I walked in and asked an employee behind their buyback counter about any new retro games that came in, and the goofy employee literally ran over to me and started yelling at me to stop asking. I was shocked that an employee was yelling at me. Instead of getting upset I asked to speak with a manager and eventually got one, but the manager didn't seem to give two shits that his employee just verbally thrashed me. At this point I was fairly pissed off, however there was a cart behind the counter that was barely within arms reach from my side that had some pretty nice Gamecube and PS1 titles on it. Mind you that these games were priced, but none of them would have ever made it out with the employees working there. I waited for a chance and when no one was looking i grabbed them and hung onto them while I continued to shop, however I wanted to make sure something happened while I was still there. I found the asshole employee that yelled at me and I made sure he could see the games i had, and holy crap you could just see the anger and hatred on his face when he saw what I had. I thought he was going to accost me again, but instead proceeded to look butt hurt. I ended up buying those games and was victorious that night. Unfortunately I barely found anything else there for the following two years until Hastings went under and so did that store in 2016, but by then it was hard for me to feel any sense of loss since that place stopped being worth it years prior.