I've not been on the site long (about 3 years) so the ones that I remember are the ones that particularly took off usually for being batshit.
The Hairdresser One
OP was a hairdresser. Her friend was on the PTA at a school. Hairdresser had no connection to the school. Friend offered up a free cut and blow at OPs salon as a PTA raffle prize without asking OP and with absolutely no intention of reimbursing her costs
She ranted and raved at the injustice when OP refused
MIL and the hat
OP had bought her child an expensive sounding hat and coat matching set. Hat went missing, and OP frantically asked MIL to keep an eye, and frequently lamented the loss MIL denied even seeing it. A long while later, OP walked straight into MIL and other DGD who was wearing said hat. Reason given : MIL felt OPs DD had too many nice things
Teddy Bear Custody
A woman was expecting a child with a man with a ridiculous over attachment to a teddy bear which had a name and several outfits. It had been bought for him by an old girlfriend. A separate ex girlfriend continued to regularly contact him for access time with this bear as though a pet or child, including holiday and Christmas visits
SIL and the Dog
OP had a 1 yo, SIL had a dog she insisted the dog be treated as an equal to the child and refused to attend his birthday because she couldn't bring the dog.
Situation With My Colleague
And a nice, none batshit one. Woman was in love with Rumpled, her colleague. She stopped the thread as it was getting intrusive but I believe they did get together in the end.