What was your most glorious revenge on someone?

OK, this is inspired by the practical joke thread, but somehow revenge can take on a much different flavor of cunning/evil.

Mine was way back when I was throwing papers as a teenager, back when they still allowed kids on bikes to have paper routes. Usually, 4~6 kids would make up a 'station', and that's where they'd drop off the papers for us. Wednesdays and Sundays always came in two different deliveries, the middle section with the ads and coupons came first, then the headline section later in the night. Well, I noticed that our station was always short about twenty papers or so on Sundays, and doing a bit of digging, I find out that two brothers at our station were sneaking to the station early, taking twenty extras, counting out their own and taking them to an undisclosed location to 'protect' them. After their route, they'd take the extras they stole, and sell them outside the local coffee shop to make pure profit on these papers. This left the last guy to show up short, and it took forever to get replacements. It sucked when all you want to do is get your route down and go back to bed.

Anyhow, I complained to the management, but they couldn't do much about it unless they caught them red-handed. I actually did catch the brothers in the act, but I couldn't persuade anyone to do anything about it. I wasn't adverse to resorting to violence, but I really didn't want to deal with the repercussions of that. One Sunday, as the brothers were getting their stuff ready, one had started to take their headline sections away for safe keeping, and the other one left to take a leak. Well, the station was on a sidewalk next to some gravel, and cats would occasionally use the gravel as a litter box. While the brothers weren't guarding their middle sections, I quickly dug up about five pieces of fresh cat shit and smeared it deeply into the coupon sections of about five papers. The beauty of this is that 1) they didn't think to protect these sections because without the headlines, they're worthless, 2) This was their delivery route papers, the ones that would get placed on doorsteps, and 3) the large portion of their customer base was retirees who LOVED clipping coupons.

Anyhow, the very next day, the brothers got notices that they had lost six customers, and to not deliver them any longer. (Not sure how it was six, I can only assume that one of the five unlucky recipients told another customer) Management did start asking questions about that incident, but all they got out of the other carriers at that station was how we were always short on Sundays, the brothers were on the take, we had seen it, and management hadn't done anything about it. The brothers were given a harsh warning, the manager actually told me that 'he understood' how something like the cat shit incident could happen given the circumstances and dropped it. We were never short a single paper again.