I had a client where I had gotten in the habits of sending over the deliverables and iterating them until they were correct (technical drawings). At one point, the client got the drawing they needed and decided they were not going to pay me.
Since he was not going to pay me, I was not going to return any of the collateral or documentation he gave me on his “top secret” idea until he did.
Instead of doing what a normal person would do with paying and moving on, they decided to hit me with a summons suing me for $10k for espionage and intellectual property theft, all kinds of fun stuff.
It went back and forth for a while and I had to lawyer up. Both lawyers realized the guy was off his rocker, and finally agreed to settle. What is annoying is the legal fees ended up being more than the couple hundred bucks for the last round of drawing changes. I had a provision in my contract/Master Service Agreement which said he would have to pay for legal fees in the case of us going to court, and I probably would have easily won. But it simply was not worth the time or money or headache.