How did you get back at an evil landlord?

I know many people out there don't get even or aren't cynical, maybe it's a New Yorker thing. But I have heard some stories from people who have put up with HORRIBLE landlords and how they got their vengeance when they moved. So, how did you get back at your evil landlord when you moved? Any tricks, stories, pranks, or mature mannered way you told them off for making your life hell?