Change their profile photo (github/slack/etc).
Flip their monitor orientation.
Swap to left-handed mouse buttons (or vice-versa).
Go on Amazon and add some "interesting" things to their wishlist/cart.
Go on Youtube and "like" a bunch of random videos.
When the …mark… sits down, inevitably with several… "witnesses" behind them, who then point out in "astonishment" the folder on their desktop, they try (in vain) to highlight it to delete it.
(Not appropriate for the workplace, of course.)
Also, scotch tape is not transparent to optical mice? and blocks the sensor. Had that one pulled on me once, took a while to figure it out.
I can tell you, that person never left that thing unlocked ever again.
alias ls=echo "Segmentation Fault" source ~/.bashrcIt took several months for him to catch on; for a while I had him convinced that his hardware must have an issue where the laptop being left idle for too long caused it to mess up somehow.
I can think of other broadcast communications that would get people fired.