We picked up a new customer a few weeks ago who turns out to a totally demanding nutcase. Like the whole world revolved around her "important" schedule. So she brings in her total POS car and expected some sort of miracle. We are a garage - not a church! Anyway, we gave her an estimate of what it would cost, etc. That evening she leaves a completely insane and rude message at the shop claiming we "overcharged her" etc. It was total BS, in fact I felt that DH did not charge her enough in the first place!
A few days later, as son as DH opens up, she is there. Ranting and raving that they messed up her car, she never had this problem till bring it here, etc. It turned out to completely unrelated to the work DH had done, and was issue, that DH could never have foreseen. However, it would take a few hours to get it straightened out. So the she started Stopping around the shop, foaming at the mouth & screaming "You are going to cost me my job!!!!"
DH just wanted to get her the hell out of there - and at that point her car was not safe to drive.
For some reason we had switched cars that day, so he gives this lunatic MY car!

Her car was done in an hour, so DH calls her and tells her to come back and give him his car back and take hers. She says: "No Way! This car is awesome, so fun to drive, I am just gonna keep it!: DS says: "Ya, well if try to do that, my wife will strangle me." She says: "Well that wouldn't be so bad HEHEHE." DS said: "Well when she is done strangling me, next she will hunt you down and strangle you too, then take her car back."

So an hour later she finally shows up with my car, telling DS she "Filled" the tank. Um, ya, I filled the tank on the way home from work the prior day. So the only way it could have needed gas was if she was driving like a maniac all over the place. I had reset the trip meter when I filled it up because I am tracking my MPG - she put 75 miles on my car in 2 hours! Plus the whole car is covered in Mud!
NO-One drives my car! EVER! Especially some crazy, now banned customer, that we have now been warned about by all the other garages in the area!
After all of that, the psycho tried to get another car towed to us today. I told the Tow Guy "Sorry, but we are not willing to do any more work for her - so take it back wherever you found it!" I refuse to deal with people like that.