Once with a room mate in England many years ago -> I seriously restructured his nose.
Once with a company that sold me a defective laptop and refused to get it fixed -> I Molotov cocktailed the building.
Once a woman rear-ended me and gave me false name and address to sneak out of the payment. I found her through the registration number, Molotov cocktailed the car and smashed her jawbone with a bicycle handlebar.
Once a client took me to court to recover his money on a project he didn't implement four years after the project was completed. I offered a conditional guarantee but the judge turned it into an unconditional money back guarantee, and I was dinged for $11,000. Sadly, this happened in Canada and here FJ (Fist Justice) is not allowed. So, I lost the $11K. Oh, well.