Office pranks are all good and fun, but there are very few times you can actually get away with something devious. Normally there is some sort of trademark like bright colors, or loud sounds that are associated with pranks. If you really want to get under someone’s skin, and not have to own up to anything, you can get a hold of the Wrongulator.

This may look like any other ordinary solar LCD calculator, but oh no, it’s something much worse. The Wrongulator was designed to give you the incorrect answer every single time. What may seem like a simple math problem to your coworkers will automatically become a mind game, with problems that yield answers such as �10 + 5 = 10�. For only $7, you can slip this into a coworkers desk and write it off as a gift from someone else. Then you can smile from your desk while panic ensues.