In the 1951 sci-fi classic "The Day the Earth Stood Still," (remade in 2008 with Keanu Reeves in the lead role), the intimidating robot comes from another world, not ours. But in way, humans are still responsible for its threat. A crisis begins when a flying saucer lands in Washington, D.C., and an extraterrestrial ambassador named Klaatu (portrayed by Michael Rennie) emerges on what he intends as a mission of friendship. He's promptly shot by a trigger-happy human soldier. That sends Klaatu's robotic assistant, Gort, into action.
You don't want to mess with Gort, and not just because he's a silvery behemoth so imposing that he makes Shaquille O'Neil look like Mini Me from the "Austin Powers" movies. Gort wears a visor equipped with a disintegrating ray gun capable of turning the armaments wielded by puny humans into wisps of vapor. We bone-bags are pretty much helpless against him, and that's the whole point. At the climax of the movie, soldiers again attack Klaatu and apparently kill him, only to see him revived by Gort's mysterious, vaguely defined powers. But Gort, probably the most recognizable sci-fi robot after the Terminator, is more of a deterrent killer robot than an evil one -- at the end of movie, the aliens inform Earth that he and other killer robots are being left in place around Earth to deter human aggressiveness, and that if we try to extend our murderous ways into space, they're empowered to wipe out humanity.
As sci-fi historians Michelle Le Blanc and Colin Odell write, "This paradox is one of many that typify the film -- the threat of unimaginable violence as a means to prevent war" [source: Westfahl].