The NACAID grim reaper ads from 1987 were enough to make people link homosexuals to Death ever since, despite there being the message that aids does not affect just homosexuals.
Most, if not all negative campaign ads run on this. The archetype example is this ad. If you don't vote for Lyndon Johnson your little girl will be blown to smithereens!!
Another great example would be this ad or the famous Revolving Door ad. But these were more subtle. If you vote for Michael Dukakis, you and/or someone you love will be raped and murdered after President Dukakis personally sets every violent criminal in the country free!
There was a Pepsi commercial back in the early 90s where a boy was on the beach sucking Pepsi out of a glass bottle through a straw. As he sucks to get the last little drops from the bottle, he somehow gets sucked into the bottle, and we see him squashed up while his sister yells "MOM, he did it again!" Who would have thought straws could be so dangerous?
And then there was the old "What's the worst that could happen?" advert for Dr. Pepper where, upon opening a fridge at a grocery store to get a Dr. Pepper, the wall collapses and an emergency unit must rescue a boy by stripping him of his clothes in front of several girls, after which he is more or less paraded around town to everyone's amusement and put on TV.
The commercials for the Virtual Boy had the system sprouting spindly legs, growing 10 feet tall, and stalking the obviously frightened kid through a post-apocalyptic world while the announcer states how, despite having its own brain, voice, and legs, it needs "your eyes." It ends with the kid being cornered, wrapped up in the controller cord, and yanked from his hiding spot to be forced to stick his head into the device and play it. Hideously creepy, especially when you consider one of the major downsides to the system was eye strain, headaches, and neck pains.
Interestingly, scary commercials were parodied in an advertisement for Sprite. It showed a mom about to serve her two kids a Brand X citrus beverage, when the mascot (a hideous CG-animated sun) leapt off the packaging and started to extol its flavor and vitamin content. All three screamed and ran, as it chased them trying to encourage them to drink up. When the mother tripped, and she urged her children to keep going and save themselves as the mascot nearly caught up to her, it might've crossed over the thin line between parody and actual horror. Even the dog was scared.
Levi's managed to get into the act advertising jeans. One of the scruffily handsome young men these things always seem to feature takes a pair of jeans off a store's mannequin. The mannequin proceeds to stalk him around town, we see it looking into his house from just outside on a stormy night. It isn't a particularly lifelike mannequin, just white with a fairly minimalist face, but we're not sure whether that makes it better or worse... Meanwhile, Screamin' Jay Hawkins' version of "I Put a Spell on You" blares out.
Not an ad so much as a logo, but Sherman Williams Paints seems rather sinister. A globe coated with blood-red paint and bearing the words "COVER THE EARTH" can't possibly stand for a company without some sinister hidden agenda. It can't be a good sign.
This demented ad for Folger's coffee, where happy sunshine sprites annoy a neighborhood full of people into greeting the new day. It's very clearly supposed to be funny, but it comes across more like a first draft of Stephen King's The Langoliers that was rejected for being too terrifying. The highlight of said commercial are the lyrics "You can sleep when you are dead!"
The creepiest parts are where the sprites (who're a real number in and of themselves) are sneaking up on sleeping people with huge grins on their faces that scream BAD TOUCH IS IMMINENT. Oh, and the sprites can enter your house silently, by coming through the glass in your windows.
Some years back, Budweiser had a series of commercials for Bud Ice featuring an eerie singing penguin who stole beer. With that creepy fixed stare and a voice that made the refrain "Doobie doobie doo..." downright ominous, it's not hard to imagine it was after your soul as well. "Beware the penguins", indeed!
That short-lived series of Volkswagen ads featuring "the Fast" is creepy as all get-out.
Good gods, they've got the police!. And it's even creepier when the sound is originally set loud enough for the subconscious, but too quiet for conscious hearing...
The Ballpark Franks TV ads with the tagline "Hunger gets what Hunger wants". A huge, apparently self-aware, arm bursts out of people's stomachs to feed itself. In one commercial, the hunger-arm chokes its "owner" to make him comply with hunger. None of this goes away in the magazine/comic page ads either, even though they're not moving. It's still creepy.
A super bowl commercial for Hulu outright tells you that Hollywood actors are in fact aliens using TV to turn our brains into mush so they can be eaten. More in the same series have since been aired.
One daytime commercial for heartburn medicine featured a man eating a lobster, then going to bed. He wakes up to find that, to his horror, the lobster was alive and coming out of his stomach with lots of blood and details.
The Burger King ads. A man walks through a dark and abandoned parking lot (Or possibly a subway. Haven't seen it in a while) when up pops a man dressed in kings robes and a plastic mask. Sound harmless enough? You've clearly never seen the mask this guy is wearing. He then offers the man food, bringing up uncomfortable "Sweets from a stranger" connotations. And he's unerringly silent the whole time.
There's been one since where the man wakes up and starts in surprise that the King is in his bed. The tray of food (breakfast sandwich, hash browns, unspilt drink) only help to add fuel to the "you don't notice him until he wants you to notice him" paranoia.
They've got a new one with the tagline "Don't go to bed before the King" where some poor unsuspecting person is sleeping only to be woken up by the King pulling some prank on them, like setting off an air horn or something. OH GOD, HE KNOWS WHERE YOU LIVE AND WHEN YOU'RE ASLEEP.
The first ad was the creepiest: the guy goes over to the door to look out and sees the king a hundred feet away, just standing there (pretty creepy on its own), then the guy turns away and looks back and the king is RIGHT IN FRONT OF THE DOOR
... And now there's an ad where the King apparently goes mad and attacks a bunch of people in an office building. Security chases him, shouting "This King is crazy!". Let the nightmares begin.
During the run of BK commercials tying in with Revenge of the Sith, Darth Vader opens his personal compartment and finds the King there. Mask and filter or no, you can tell the Sith Lord is creeped out.
The Geico commercials with the money with eyes even has the "Somebody's Watching Me" song in the background.
Invoked in the Brinks/Broadview Security ads, all of which feature some thug kicking down the doors or sneaking into the a home where some woman is all alone, only to be scared off by the alarm. Oddly enough, the women and perps are all white, presumably to avoid Unfortunate Implications. One has the husband pass a jogger on his way to work, a jogger who promptly puts up his hood and knocks the front door down. Another has a mother and her daughter playing in the backyard, with the creepy mofo watching through a hole in their garden gate. He attacks seconds after they walk inside and close the door. Another is the woman's ex-boyfriend, who is waiting for her outside when she comes home from a date. The premise is presumably to make women wet themselves in terror and buy Broadview Security.
One has to wonder how the invaders managed to miss the signs and stickers that would undoubtedly warn of the security system. Plus the noise one would make kicking in a door. And the sheer stupidity of invading a home with people inside. (Yes, it's hard to take those commercials seriously having watched It Takes a Thief (2005))
The worst is probably the one with the woman on the treadmill. There's no possible way of ignoring the rape connotations—he's not breaking into a house with lights on and a jogging woman just to rob it...
Possibly, the "got milk?" ad that featured Product Placement for Super Mario 64. Remember, kids: If video game characters want to, they'll come out of the game through your TV and raid your fridge!! (So don't fall asleep while playing Silent Hill or some other horror game... pleasant dreams otherwise!! 0_0)
An advert for Batchelors "Cup a Soup" involved the "hug monster". If you eat/drink a cup of this soup, a big pair of blue hairy arms will hunt you down and tackle you from behind before feeling you up. "It's like a hug in a mug".
Adverts for surface cleaners or food hygene PSAs tend to use this, usually by showing a virus making it's way from a sneeze onto food and stopping just before someone (usually an infant) eats it.
TV ad where baby says "Hi TV" is creepy. It's like "The Veldt", a Ray Bradbury story that didn't end well at all.
Pro Golfer Phil Mickelson says "If you have painful, swollen joints, I've been in your shoes". Well keep your diseased feet out my shoes!
Andro-gel testosterone cream, the 1st treatment to warn you of side effects in YOUR FAMILY! Early puberty in your kids, a beard on your wife.
This series of ads for Panda Cheese will make you paranoid that a vindictive panda will show up out of nowhere and ruin your life should you ever refuse to eat his cheese. The tagline? "Never say no to Panda."
This trope is part of the reason why Sega Saturn succeeded in Japan. Because God help you if you do not have the console, a judoka named Segata Sanshiro will come and beat the ever loving crap out of you. It doesn't matter if your 'crime' is having another console, or playing non-video games like baseball, or even doing some entertainment that is not a game, quote the tagline, "You must play Sega Saturn/Sega Saturn, Shiro!!"
One very ill-advised campaign for mental health awareness in the early nineties featured a video advert that would play quiet whispering sounds while you browsed the webpage it was on. Only finding and hovering over the advert would reveal it as the source: an attempt to raise awareness about paranoia.