I really pissed my roommate off today...his computer has an nVidia graphics board in it, so when he was at work I went into his display settings and used the NVRotate feature to flip his screen upside down! I came home from work and he had his monitor upside down...of course he started yelling at me as soon as I walked in
*I* thought it was funny anyway...
Anyone else like to stuff like that to other peoples computers?
Some ideas:
Replace their wallpaper with a screenshot of their desktop, and move all the icons...
Plug a cordless mouse/trackball into their system and move their curser around whenever they try to click on something...