Taser
They are hand-held weapons that deliver a jolt of electricity — up to 50,000 volts — from up to 10.6 metres away. The shot can penetrate up to five centimetres of clothing. 

It stuns the target by causing an uncontrollable contraction of the muscle tissue. He/she is immobilized and falls to the ground — regardless of pain tolerance or mental focus. 

TASER stands for Thomas A. Swift Electric Rifle, from the Tom Swift series of children's novels written in the early 20th century, including Tom Swift and his Electric Rifle. The real stars of the series of science-fiction novels were potential advances in technology. 

from "cbc news" 
Canadian police say Tasers have saved 4,000 lives since police forces started using them in this country in 1999.