Circuit of a taser, with a 555 timer. This taser will have a output of 50 kV, and is powered by a 9 volt battery.
A little bit of history of the Taser:
Jack Cover, a NASA researcher, began developing the Taser in 1969. By 1974, Cover had completed the device, which he named after his childhood hero Tom Swift ("Thomas A. Swift's Electric Rifle").