I hid money on my incompetent manager and let him think he was going to be fired
This is an old story from like 7 or 8 years ago when I was in my mid 20's. I worked as a second in command (2IC) in a retail chain store for about 4 years. The first year was great until our amazing manager was let go because they couldn't work full time anymore. For the next 3 years I worked there, we had the most incompetent manager. He was a nice enough guy and we could chat gaming for hours, but he was just useless at his job. He probably bordered on being a neckbeard thinking back on it. He had manager experience but no retail experience and would generally just waste time moving stock on shelves or racks that didn't need to be moved for the 10th time that month. He generally took forever with his manager duties and on the days he was away and I had to take over, I could get his work done in half the time. If I'd known I would be doing more than half his work when our old manager was let go, I would have put my hand up for the job but I didn't think I had enough experience at the time. His worst flaw by far was leaving the safe open or leaving bank slips full of cash on the desk in the warehouse and leaving the room to go take care of other business or personal phone calls. This happened at least a half dozen times I can recall.
For a bit of added context, the back desk in the warehouse was only about 10 meters away from our service entrance and we had delivery drivers and couriers in and out all day. These drivers could easily see this desk and the cash sitting on it if they looked close enough. The desk is also just outside the camera FOV but the service entrance is still in view. Directly next to this desk is our floor entrance from our shop and is only blocked by an opaque plastic door. A customer could easily stick their head in there without anyone knowing. Its a miracle that no money has ever been stolen before. Why they didn't put a computer in the back room where the safe is, I'll never know.
On to the petty revenge. One day I am walking past the back desk in our warehouse and I see about 4 or 5 bank slips with cash in them from each day of trade. Manager is nowhere to be found (probably taking a 30 minute morning dump like he usually does). I get the bright idea to casually knock one of the bank slips behind the desk. I did let one of my other colleagues in on the plan who was also over his incompetence. He finally comes back after maybe another 10 minutes and returns to finishing up the banking. I start to see him walking back and forth between the desk and the room where the safe is. The desk and the safe are on almost complete opposite ends of the shop. I can see the worried look on his face. I call out and ask him what's wrong. He finally admits that he has lost one of the bank slips. He knows it was lost since he has the paperwork and he has processed it in the computer but just hasn't put it away ready to be taken to the bank. He knows he's in deep trouble now because he's going to have to admit money has gone missing because its been left on the desk unattended. The correct process is to put it back in the safe and lock it if you aren't actively working on it.
I'm telling him how dumb it was to leave the money there and with delivery drivers coming back and forth, it could easily have been stolen. Or maybe it was an opportunistic customer who just happened to take a peek behind the warehouse doors. Its starting to really sink in now that he's going to have to explain all this to management. I'm making a few casual comments to my other colleague asking if they think its a fireable offence just to really twist the knife. Part of me still cant believe he hasn't checked behind the desk.
He realizes that the camera must have caught someone entering the warehouse in that time so he spends the next 30 minutes going over all the camera footage. I knew I was safe since the desk isn't in the camera FOV and me being in the warehouse is hardly uncommon. I can see the gears turning in his head that if he claims the money was stolen, he might be able to gloss over how he left the money out for all to see.
He finds nothing on the cameras and is pacing up and down. My other colleague I let in on my little prank is now reiterating everything I have told him. Its been about 45 minutes since he discovered the money was missing and he's getting ready to call our area manager to explain the situation and ask him what to do. He looks like he's about to have a panic attack. Finally my colleague thinks he's stewed enough and decides to "find" the money that has mysteriously slipped behind the desk. The relief that washes over him is completely visible. I personally would have let him explain it to upper management, then found the money, but my colleague is apparently much nicer than I am. After seeing him leave money in the open at least a half dozen times, I was happy to have him see some consequences for admitting to leaving money completely unsupervised.
Everything was resolved, upper management never knew and my prank was never discovered. Probably not the juiciest story out there but it was very satisfying at the time after years of pent up frustration. He never left money out for the entire time I worked there after that, so I hope it taught him an important lesson in responsibility and just common sense. I have a few other good stories of his incompetence but nothing else that involves revenge.