A few years ago, when I was in high school, we had a teacher who would take a quiz every week. This particular teacher would attach his laptop to the projector and then show us the questions on a slideshow. Each slide had an exact amount of time depending on how hard the question was and we had to write the answer on a paper. One week, we also had another exam so neither of us had studied for the quiz. One of my friends who had another class with this teacher, told us that their projector stopped working, so the teacher didn't take the quiz and it was postponed. Since most of the class agreed to postpone the quiz, we decided to sabotage the projector so the teacher would be forced to postpone the quiz. We couldn't actually harm the projector because we would get in trouble, so one of my taller classmates stood on a chair so that she would reach the projector. Then she slipped a small piece of paper between the hdmi/vga cable and the port located on the projector. That way it seemed like it was connected but in reality it was not.
The teacher came, could not connect his laptop to the projector, so no quiz!
Sorry, teacher!

P.S. We reverted the changes the next day. Blamed the cheap cable for short circuiting!