Desktop shortcuts are a great way of making the programs you use a lot more accessible, but today many PC users overuse their desktop space and have icons covering over half the screen, including the one for a picture of a dog they looked at six months ago once. This prank is a great way to teach such a person a lesson, or any PC user who you have a problem with. It entails creating a new desktop shortcut with the name and icon of a commonly used program (the web browser works great) that instead of executing the program will instead display a custom message, then turn off the computer automatically after an amount of time that you set. It won't hurt much and creates a very scary effect, scalable based on what you enter into the custom text box.
Here's the text that you use as the destination of the shortcut, when prompted:
shutdown -s -t 60 -c "write anything here"
Except you write anything in the write anything here part.