When I was in high school (in Slovenia), I have actually brought a home-made "bomb" to school. It had an LCD and a keypad, you would arm it and it would count d

When I was in high school (in Slovenia), I have actually brought a home-made "bomb" to school. It had an LCD and a keypad, you would arm it and it would count down while beeping with increasing frequency, unless you entered the correct deactivation code. Nobody mistook it for a real bomb and nobody had any trouble with it, except for when it was set up in the middle of class to annoy the teacher :) A later improvement was the addition of "detorator circuit" based on the flash electronics for a disposable camera, and you could hook up something like a resistor to it which would then be fried by who knows how many volts...