In a recent post Raymond Chen talks about Big Red Switches and various people weigh in with recollections about pressing such things. Well, I have in my possession a Big Red Button that I found at the excellent Triangle Machinery & Tool Co in San Jose. When I had a desk, I used to have it mounted with a thick cable running from it to under my desk. It wasn't connected to anything but it told me lots about the people around me.
Most people would ask "what's that for?" or "is it connected?", but occasionally there would be someone who would press the button and then ask the same questions. Those are the people you should never let into a server room!