I've had this debate with some coworks. What voltage (rough order of magnitute) is used to safely shock people?
"Safe" is a vague term, but as an example, there are arcade games where you hold onto two rods and you are hit with a jolt that grows in intensity (the challenge being to hold on until the end). I've also seen this sort of thing at museum where you touch two contacts to "feel the jolt of an electric eel". Not painful, but you definatley feel some force going through you.
Right now, due to different interpretations of some fundamental laws of electricity, we have guesses of "about 40 volts" and "about 40,000 volts", so please explain why one value is used over another.