If we wanted to knock someone out from a distance, we could always throw a rock at their head, and killing really is simple enough when you’ve got a .44 magnum. But what about a laser gun that kills and stuns? Gene Roddenberry pandered to both the Sixties generation Star Trek was conceived in and the growing public appetite for science-fiction gadgetry by giving his characters the Phaser: a gun with a gradient slider that could turn its relatively harmless stun beam into an absolutely lethal killing weapon. Just be sure to put it on the right setting though, eh?