What's the pettiest revenge you've ever seen?

My neighbor kept stealing my parking spot despite the fact that I pay for it monthly. After politely asking him to stop multiple times, I got fed up. One night, I filled a spray bottle with water and fish sauce, then lightly sprayed his car handles. By morning, the stench was unbearable. He stopped parking in my spot the very next day. Petty? Yes. Effective? Absolutely.