I just rub my signs with Poison Ivy, then look to see which neighbors or their kids are covered in Calamine Lotion. Make them pay by being extremely uncomfortable!
Only problem with that is the perp may not be allergic to poison ivy and it’s doubtful they’ll make the mental connection so it will have no preventive effect. Plus, no one is on their first exposure to it, so it’s unlikely to get results if the perp is a kid whose life consists of school and video games in the kitchen. Others can roll in it on every camping trip and not have a reaction until, say, the 51st time.
Now ghost pepper juice in vegetable oil?
The electric fence is a great idea- instant correction- and it won’t hurt them.
But even a thick coat of petroleum jelly or tanglefoot might be fun- they’ll get nice and sticky and stay that way until they can wash their hands.