Emergency power off
First job working in the comp sci department at a well-known technology-focused university in London. Annually we'd show prospective students around the facilities including the server rooms. There were big red emergency power-off buttons in various places. A particularly tall budding student decides to lean back against the wall and... These were the days of IBM 4331s, various DEC servers, a big ICL mainframe and others. Generally things didn't tend to work well after a sudden power-off.