(Yes, that's right, 2 posts in one night!! Apparently the juices are flowing! Hardeharhar.)
Some very unhappy facts have come to light about the husband of a friend of mine. This calls to mind some deliciously wicked tales of revenge that happened to a family friend (and were deserved, at least to some extent).
This person (let's call him E) had recently broken up with his girlfriend (X), and I believe cheating was involved. Somehow or another, he totally pissed her off. So she did the following:
1. Called 911 at about 1:00 in the morning, reporting in a panic that E was having a heart attack and was able to contact X but would not be able to get to the door. So, naturally, the ambulance and EMTs show up, bust down his door, come charging into the house to find E with his new woman, recently woken from a sound sleep. Some serious persuasion was required to convince the medical personnel that E was not, in fact, having a heart attack, and that they should stop trying to resuscitate him.
2. X posted E's car for sale in the local newspaper, mentioning in the ad that the owner of the car worked a weird shift, so calls would only be answered between 1:30 and 3:30 in the morning. I have no idea how long it was before E figured out what was going on and pulled the ad.
Other favorites of mine include mailing a favorite item of the intended recipient of revenge to that person, spread across several packages, preferably first smashed *almost* beyond recognition. Of course, this does require postage. However, if you of the mind to get creative with annoying your target, and money isn't really an object, this may be a worthwhile read: Postal Experiments. Of course, even if you aren't in the market for revenge, it is a pretty entertaining way to pass some time, especially since photographs are included! I also once heard a highly amusing podcast about experiments with the postal service, either through Podcastle or Escape Pod, I can't really remember which, that I think was somehow related to the above link, maybe just inspired by it.