When I was in high school, the IT had the bright idea to use the same username/password for each machine in our site, and there was this jerk who knowing this, would occasionally SSH into the computers of the other classmates and wget porn mp4s to their home directory to embarrass them, as some sort of weird-ass prank.

So, in order to give him a lesson, I one day had logged in and set a rule on the class' router to forward all port 22 traffic back to his own IP address, and had SSHed into his machine, aliasing wget with a full-screen kiosk mode chrome, followed by a force disable of the USB HID devices.

It might have been less awkward and he might have seen less scared, if it wasn't for the fact that I had also remotely set his machine to maximum volume, and the teacher wasn't in the middle of a lecture. 😏

To this date, his expression is the most precious reaction I have ever seen.