Many moons ago, I worked summers in college at ATV/motorcycle/boat dealerships. We had all sorts of interesting characters come through.
A customer came in one day wanting to buy a very expensive Crownline boat, with cash. He had a gorgeous blonde on his arm, and a fresh, still bleeding, tattoo on his leg. Turns out he'd just won some sort of settlement, and it was time to go shopping.
Another day a young man came into the shop and purchased a Kawasaki street bike, with cash he'd apparently saved up for a while. When the deal was done, one of the mechanics rolled the bike around to the shop for oil, gas, etc. After the final prep, the young man fired up the motorcycle, said goodbye to his pretty girlfriend, turned right out of the shop....and laid the bike on its side. Turns out the kid had never ridden a motorcycle before, and he had the nerve to ask the dealership's owner if he would give the kid his money back on the bike. Uh, no.
Our dealership sold Kawasakis and Suzukis, but there was a Honda/Yamaha shop on the other side of town. I was stunned at how many customers would come in, throw a random part (or better yet, a cable) on the counter and say "you got one of these?" More often than not the customer would have no clue what kind of machine he had ("Well, it's red...") or, better yet, the customer knew he had a Honda/Yamaha and just didn't want to drive across town.
This is my favorite customer story, though. One day a young man came in wanting to buy a "brain box" for a Kawasaki Mule. He was convinced he needed one, and wanted it ASAP. Of course, he didn't have any idea what year model Mule he had, and as fate would have it, the part numbers were different for his best guesses on the year model. We didn't keep these "brain boxes" in stock because they were around $600-700 each, and being both an electronic and special order item, there were absolutely no returns. We made all this clear to him, and he insisted on ordering one overnight, signed the ticket, and away we went. Next day he came to pick up the part. A few days later... the young man comes back into the store wanting to return the brain box; it didn't fix his problem. We reminded him of the no return policy, and showed him the ticket he signed acknowledging the policy. So of course he pulls out his cell phone to call his father, and then he tries passing the phone to me to talk to his father. This was beyond my paygrade, so I went and got the shop owner. He talked to the father, informing him of the return policy, and shortly thereafter the young man stormed out of the store. I kid you not, though: a week after that the young man came back into the store trying to return the brain box again, as if we didn't remember him. Of course we turned him down again, and he left without a fight.
Another time a customer brought in an ATV, saying the engine wouldn't start. The mechanics tore it down, and it turns out the engine was full of mud. The young man had been "mudding" the ATV and sucked mud into the air intake, ruining the engine. They fixed it, though, to the tune of several thousand $$. Within 2 weeks, the ATV was brought back into the shop again for the exact same problem. Both times the young man's father showed up and just wrote checks for the charges.
And finally...a parts guy who'd worked at another dealership once told me a story. Summertime is crazy for the repair shop because customers bring in their boats/personal watercraft for repairs, and obviously they want the vehicles back ASAP. The owner of this other shop got sick of customers complaining about the long repair times due to volume, so he implemented a new policy: we'll put your vehicle to the front of the line if you're willing to pay double price for the parts and extra for overnight shipping. My friend said he was shocked at how many impatient customers took advantage of the offer. Wow.