Offending Parties: Demon Seed, Maximum Overdrive, Chopping Mall, Ghost in the Machine, The X-Files: "Blood", The Mangler
The concept that our reliance on technology could be our undoing is a potent plot device, and one which has been used to great effect in many films. However, the notion that a machine could develop sentience and summarily become evil is amusing at best and hilarious at worst. The Stephen King story "Trucks" actually managed to execute this idea quite brilliantly, primarily because it never made its titular nemeses out to be anything other than mindless drones (albeit mindless drones that knew Morse Code and were capable of strategy). Alas, King opted to go all cartoon Apocalypse for his story's filmic adaptation, Maximum Overdrive, dispensing of the source material's subtle nuances in favor of gonzo lawnmowers and crotch-killing Pepsi machines. "The Mangler", culled from the same story collection, fared no better, its seriously disturbing imagery steam-pressed into a peerless escapade of inanity that served only to reinforce the suspicion that Tobe Hooper had blown his load with Texas Chainsaw.
Although precursors to the aforementioned psychotic Erector Sets could surely be found prior to 1968, it was HAL 9000 who really got the ball rolling. His icy descent into madness, exquisitely voiced by Douglas Rain, remains the standard by which all other sinister automatons are rightly judged. However, his example has proven impossible to top, and practically every attempt since has proven to be an embarrassment. (Of course, the Killbots in Chopping Mall weren't intended to be anything but a joke, but I kept them on the list because they got to ice Mr. Futterman from Gremlins.)
If ever you're faced with a vacuum cleaner that keeps attacking your leg or a George Foreman grill that just won't let go of your hand, I have a suggestion: Pull the plug.