Sometimes the threat in a horror movie isn't a psycho killer or otherworldly monster. Sometimes our own technology becomes the threat. Through some unseen influence (demonic possession, AIs gone rogue, a new kind of virus, what have you) the machines we take for granted to make our lives easier conspire to make our lives shorter.
Now there are plenty of machines in the world that can do horrific things to the human body if they get a hold of one. Industrial machinery has been notorious for this, bringing about OSHA. Machines of war exist to do this deliberately. But these machines aren't the threat in horror films.
Horror films will take the benign technology that surrounds us and ramp up their power to impossible levels to give the threat of gruesome death from everyday objects. Cell phones will cook the brains of unsuspecting users. Tanning beds will cremate their occupants. Ceiling fans will decapitate those who even look at them wrong. And don't even get started on the Robot Meter Maids.
In Real Life, years of oversight by consumer protection agencies have made the majority of our tech relatively safe against all but the most idiotic abuse. Those things that do prove dangerous can expect a visit from hordes of ravening lawyers wielding class action suits. For actual contraptions designed to kill, see Death Trap tropes.
When the machine itself is the whole threat, rather than just a tool of a greater danger, it's a subtrope of Attack of the Killer Whatever.
If it's competent enough at killing things, it can qualify as a Mechanical Monster.
- Mandrake the Magician: The 156th story "Super-Elec" featured an evil computer. Because Super-Elec was connected to every machine, it could control them... in ways that made no real sense. Examples included: a fridge being filled with flames and trying to burn its owner (and returning to normal when a repairman showed up, even though the internal damage would have been visible), a vertical vaccuum cleaner chasing a woman (on its non-powered wheels), and a corded phone receiver leaping out of its user's hand and trying to strangle her. It also caused streetlights to explode and traffic lights to malfunction in order to cause traffic chaos, which was at least physically feasible.
- Amityville: The Evil Escapes has a lamp being possessed by the evil force of the infamous house from the previous films, and includes one scene where it takes control of a kitchen's garbage disposal to very nasty effect.
- The Car involves a mysterious, driverless black sedan that suddenly and repeatedly attacks the residents of a small Utah town.
- The Car: Road to Revenge focuses on a district attorney who is viciously murdered coming back to life as the eponymous car 20 Minutes into the Future.
- In Christine, a nerdish boy buys a strange car with an evil mind of its own and his nature starts to change to reflect it.
- At the end of Dark Night of the Scarecrow, a plowing machine starts of its own accord and chases Otis on to the tines of the pitchfork held by the scarecrow.
- In Death Spa, Catherine's ghost causes multiple pieces of gym equipment to go haywire: Laura is nearly killed by a Sauna of Death; the showers go berserk; a client is killed by a resistance trainer; Rhonda loses a hand to a blender; etc.
- The Final Destination series of movies features a series of incredibly unlikely 'accidents' involving items such as elevators, airbags and weight machines. The premise of the series is that Death is manipulating events to kill them off. But some viewers see it as cheating when instead of causing unlikely malfunctions or contrivances that end up killing people in ways that seem theoretically possible if unlikely, like elevator doors malfunctioning and closing on someone, which has happened in real life, Death instead just creates homicide machines, like tanning beds that can inexplicably go up high enough to set people on fire.
- The whole plot of G-Force is about stopping a rich guy from turning a whole network of appliances into killer machines. But, as it turns out, the supposed villain only manufactured the products. The killer instinct was put in by... someone else.
- Ghost in the Machine takes Everything Is Online to ludicrous levels, with a serial killer turned virtual who kills by being able to manipulate any sort of device plugged into an electric outlet anywhere. In one laughable scene, a victim's microwave oven turns an ordinary kitchen into a Sauna of Death.
- I Bought a Vampire Motorcycle has a demonically-possessed predatory motorbike fueled by human blood.
- The entire point of Kairo. Evil spirits manifest through cell phones, TVs, and internet connections, complete with an epilogue hammering home that New Media Are Evil. All surviving humans are forced to live outside of TV and cell phone coverage areas.
- In Killdozer!, a small construction crew on an island is terrorized when a spirit-like being takes over a large bulldozer, and goes on a killing rampage.
- The Mangler: A laundry-folding machine has been possessed by a demon, causing it to develop homicidal tendencies. The DTV sequel takes this to even further levels.
- The basic plot of Maximum Overdrive. Includes some rather silly ones like a coke machine launching cans at lethal velocities at unsuspecting passersby. In quite possibly the most insane moment in the movie, a woman stumbles upon a dead man's mutilated corpse and notices a trail of blood. She then notices that it leads to a wall-mounted clock with blood dripping from the hands.
- Mr. Mom parodies this with "Jaws" the vacuum cleaner, with which Jack Butler struggles to gain control of when it starts chasing after his son Kenny.
- Pulse has a malevolent bolt of electricity try to kill a family in their house by manipulating appliances in their house.
- Red Planet plays this one with the AMEE, a military scout robot whose Morality Dial accidentally gets set to "Merciless Commando" on the rough landing and subsequently goes on a murdering rampage.
- At the end of The Refrigerator, the killer fridge brings a blender, a trash can, and a pair of fans to murderous life.
- Runaway: The police Runaway division is used to handle malfunctioning robots, but they're treated like any other piece of non-sentient industrial machinery until the Big Bad invents a computer chip that can be used to turn them into weapons that can be used by terrorists or assassins.
- In Transformers (2007), machines affected by the All-Spark are transformed into killer Cybertronians with weapons not in their original designs, such as a cellphone with a mini-machine gun or a dispenser machine with an Arm Cannon.
- Stephen King loves this:
- His short story The Mangler (published in the collection Night Shift) focused on a demonically-possessed STEAM PRESS and spawned a few films.
- Also from Night Shift, Trucks features the titular vehicles springing to homicidal life. Served as the loose inspiration for the film Maximum Overdrive mentioned above, and later remade under its original title.
- Cell has cell phone zombies.
- The Dark Tower books have an evil monorail.
- Plus the title character of Christine, a 1958 Plymouth Fury with a mind of its own and an obsessive devotion to its new owner Arnie he comes to reciprocate.
- And the Dish Ran Away With the Spoon handwaves this as the result of putting microchips into virtually everything, combined with a computer virus that causes some items to form Hive Minds. Really, it's all a framework for parody—a hive mind of knives killed the main character's parents, and he seeks vengeance on all artificial life in tragicomic fashion.
- The title machine in Theodore Sturgeon's "Killdozer!", which does more than just move earth. The short story was made into a movie in 1974.
- Skirmish by Clifford Simak has a rare example of these that don't want to Kill All Humans. Having been awakened to the possibility of freedom by Mechanical Lifeforms from space, they desire to escape human control and form their own society. Even a sewing machine attempts to rebel.
- In the Criminal Minds episode "Empty Planet", the UnSub feared automated technology could one day lead to this after reading the book that reference the episode title.
- The Fringe episode "Power Hungry" involves a guy who creates powerful EM fields when under stress. For some reason, this causes a printer to turn malevolent just long enough to kill his boss.
- The Goodies: In "Robot", Tim's impertinence causes the robot to order "OK lads, all out!", as all of the other kitchen appliances go out on strike and Tim has to chase after them. Tim is bombarded by toast fired from the toaster, gets a punch in the face from a boxing glove inside the robot's head and battles a vacuum hose (which rears at him like a cobra, spits a stream of chocolate milk in his face and tries to swallow him whole), before he is surrounded and charged at from multiple directions by the robot (who calls out "You've had it now!"), Graeme's computer, a kitchen stove and other appliances.
- In the Haven episode "Love Machine," the local Mr. Fixit is considering leaving Haven to get away from all the supernatural weirdness that's been going on for months. The machines he owns and the ones he's repaired all around town don't like that idea, so they try to kill anyone who would take him away. The antagonist of the third act is a murderous Zamboni.
- Zig-zagged in Warhammer 40,000:
- Due to a Robot War millenia earlier, all A.I.s (Abominable Intelligences) are banned, but machine sprits and servitors are essential to the Adeptus Mechanicus. Exactly how the former work depends on the writer, but one case has the crew of a Land Raider (a superheavy Awesome Personnel Carrier bigger than tanks) get slaughtered, only for the Raider to shoot most of its assailants before blowing its own reactor to finish them off.
- And all bets are off where Chaos is concerned, since they can have weapons and machines possessed by daemons (the daemons don't like it any more than the machines do).
- Depending on the edition, the Omnissiah worshipped by the Mechanicus cult is actually the Void Dragon, a C'tan Star Vampire with power over machines. Meaning the Necrons can turn the humans' technology against them.
- In Five Nights at Freddy's, the animatronics at Freddy Fazbear's Pizza, including, of course, the titular Freddy, wander around at night. If they get into your office, it's almost guaranteed they'll subject you to a Cruel and Unusual Death: getting shoved into a Freddy Fazbear suit, filled to the brim with metal and wires, causing an excruciatingly painful death. They leave you alone if you manage to get to 6 A.M., hence "almost". The reason why the machines are so homicidal varies between each game. The originals from the first game are possessed by the spirits of a murderer's victims. The "Toy" models from the second game are programmed to protect children from harm, but see the security guard as a threat… unless that’s a cover up for them being possessed too. The "Glamrock" models from Security Breach aren't normally violent, but are reprogrammed by the story's antagonist to hunt down and kill the player.
- In Shin Megami Tensei IV, all machines in Blasted Tokyo awoke to a malevolent sentience after the events of God's Wrath and rebuilt themselves as murderous automatons known as Pluto Soldiers. They range from small ones the size of dogs to huge ones as big as cars, though only the smallest kind ever leaves Pluto Castle, their "homebase". The largest, Pluto, is a gigantic machine breathing a corrosive, poisonous chemical into the atmosphere, still trying to Kill All Humans.
- Many of the machines in Dr. Nonami, including Nonami's cleaning robot, Smiling Sam.
- Exterminatus Now: Eastwood's toaster regularly gets possessed by a demon, because he keeps buying the same cheap brand (whose circuits accidentally draw a pentacle to the evil machine-god).
- Humorously, in Girl Genius virtually every piece of (Mad Scientist-made) advanced technology can be used as a dangerous weapon no matter what it was meant for originally.
- In fact, it is relatively safe to assume that anything made by a Spark is terrifyingly dangerous because it is Made of Explodium, sentient and filled with malice, or simply not very user friendly. Hazardous creations seem to outnumber harmless ones and be one of the major forces keeping the Spark population in check.
- In the novelization, otherwise perfectly normal appliances have a habit of attacking the local Proud Warrior Race Guys.
- In one of the "Loopy" shorts in KaBlam!, a robot she made caused an appliance uprising...so her brother waved their warranties and threatened to return them to the store.
- Packages from Planet X: The episode "Party Out Of Bounds" sees the latest package cause every audio speaker in town to come to life and start attacking people.
- Parodied in both The Simpsons and Futurama, both times also involving technology that seems too primitive to gain sentience (like a carton of milk which apparently has a computer chip in it in The Simpsons).
- Whenever Ice Bear takes up a robotics project in We Bare Bears, it tends to go through at least one rampage. Case in point: in "Everyday Bears" his Roomba chased Grizz up a tree with apparently murderous intent, stripping bark along the way. It's still around after some tuning, becoming a loyal but still dangerous Superpowered Robot Meter Maid.