Skinsaver, imitating the blue screen of death on your computer. The main thing is that a colleague would not smash half of the office when he had to reboot the computer on which the document was open, which he did all morning, but forgot to save :)
You can also shock a colleague with a “broken” monitor. To do this, there is a special wallpaper , the main thing is not to forget to hide the icons and panels on the desktop. (cross-platform thing :))
Non-closing window
Open any window on a clean desktop, take a screenshot and post the picture as wallpaper. At least 30 seconds a colleague will try to close the drawn window :)
Lifehacker.com was partially used.By the way, there are many other interesting things.