Here's another fun computer one, open up notepad and type
shutdown -t XX -s -c "Blah blah"
The XX is the amount of time in seconds you wish to give them before the computer will shutdown, -s simply tells it to shutdown, you can alternately use -r to restart it instead, and -c is the comment, so fill in whatever fun message you want.
For example:
shutdown -t 30 -s -c "Illegal hacking detected, computer shutting down."
Note: The shutdown message cannot be very long.
(To abort said shutdown, you can either do the same thing in another text file except have the code shutdown -a or you can run cmd, your command prompt, and type in shutdown -a)
Once you have the short code line typed out to your satisfaction, simply save the file with a name the person is likely to click on and make sure you type the extension .bat
For example Readme.bat
Have fun!
(For added stealth, you can change the icon to a game icon and rename it appropriately)