Beanie Babies
Silly Bandz
Pogs
Pokemon Cards
Tamagotchi
Cabbage Patch Dolls
Furbies
Zhu Zhu Pets
You can’t talk about peer pressure driving sales without mentioning the products who only made any money at all because kids all wanted the “cool” new whatzit like the other kids have.
Not a product, but this is the model for the way Campus Crusade for Christ works. They target the athletes and the popular kids in schools and then use them as recruitment tools - “If you want to hang with the cool kids, join our group!”
Jagermeister
Oh yeah, definitely. It was a hard lesson learned: no matter how attracted you are to the guy offering it, just say no to jager. Otherwise, you and the toilet will have in-depth conversations all the next day.
Jack Daniels. The stuff is horse piss.
If you’re talking about John Deere agricultural products (tractors, plows, combines, etc.) they’re the real deal, also backed up by distribution, a strong dealer networks and all that other Marketing 101 stuff.
If you’re talking about the JD lawn and garden products, they mostly live off the reputation of the farm equipment, and unless you buy your farm equipment from a JD dealer who’ll give you a great price on a lawn tractor, there’s no real reason to pick it over, say, a Honda.
Tattoo and Piercing
SUV (particularly fair weather city folks although much less so now since gas price shot up)
Booze/drinking
Cigarettes
Chewing Tobacco for baseball players
Hair Styles (from mullets to shaved head and highlights to dark-roots-light-ends)
Starbucks
Sunglasses (Aviator to Wayfarer to whatnots)
I like Jack Daniel (though I used to hate it but I didn’t like hard drinks much then). Should I not admit it publicly?
I used to think the PBR -> hipster thing was one of pure pragmatism: PBR is cheaper than “big name” macros, but is drinkable and has a decent-looking can compared to some. Hipsters also like ironically uncool things, so picking the beer with a dumb name and no ad campaign seemed obvious.
It’s become clear that PBR actually aggressively courts hipsters, sponsoring indie rock concerts and being served in divey rock bars all over. I’ve heard that the whole thing was brilliant, intentional underground marketing designed to find a niche for a weak product.
Way to go, Pabst.
That cheap-ass mezcal with the worms in it.
I think the vast majority of their sales are from college guys who buy it on some kind of macho dare.
As someone recently in the real estate market, may I add granite countertops and stainless steel appliances? These things are gonna be the stylistic equivalent of Harvest Gold appliances and snag carpeting in a few years.
That’s the one I came in here to say. For a few years in the 2000s, and to a certain extent even nowadays, MP3 player was pretty much exclusively synonymous with iPod in the minds of a lot of people, even though there were a lot of other brands on the market.
How much was your wedding dress? 
To answer the OP, cigarettes. I can’t help but think of the episode of Roseanne when she tried to quit and she blames tv for her smoking. Saying when she was a kid EVERYONE on tv smoked. 
TV
Kitchen appliances
Weber gas grill
I knew someone would mention Apple products at some point. But I think the implied point in the OP is that the product is not as good; just that peer pressure obliges people to buy it. I would argue that Apple products are beautifully designed and tend to offer a superior user experience when compared to rival products. I own all of the iDevices, and tend to be a mid- to late-adopter… I usually balk at the price of the new stuff and I limp along with what I have until I see how kick ass the Apple stuff is, and I relent.
You nailed it on the jewelry stuff. I don’t need to show anybody my iPhone/iPad/iPod. Wedding jewelry, especially engagement rings, are expressly to show others.
I would say some makes of car - like the entry-level BMWs, I think, that are not that reliable and have cloth interiors. Or is it Mercedes-Benz?
Makeup.
Honda cars in general, maybe.
But the aftermarket, pimp my ride, hang-out-in-the-taco-bell-parking-lot-and-talk-about-street-racing crowd sure seems to flock towards the civic as if there is no other option. Hell, I remember seeing “imports” and “hondas” on the list of interests on dating site profiles years ago. I’d say that specific honda fits the OP’s requirements, selling so well because of peer pressure. The community decided that any other car just wasn’t as good, even if it was.
GMC/Dodge/Ford Trucks. Real men drive manly American pickup trucks. There was even a commercial “There is no Japanese word for pick-up truck”.
My SiL tried to pull the same stunt when she looked at my Nissan rice-burner (a pathetic Titan, no less). She huffed “We only buy American”. We checked the VINs: My car was made in Georgia, her Chevy was made in Mexico.
Power tools
Interior Design products (including Kitchen, bathroom etc)
Racing bicycles
Vacuum cleaners
Fancy washer dryer
Boats
Neighborhoods, ie, rich neighbors to not so rich
Ugg boots
I don’t think any of those really qualify here. I don’t think anyone buys a TV due to peer pressure, they buy a TV because they want to watch TV, they want/need entertainment. Kitchen appliances? You’re going to need to expand on that. Unless you have a way to cook chicken, boil water or freeze ice cream with out kitchen appliances, I’d consider them a necessity in life. And as for Weber Gas Grills, they truly are high quality and more then worth the extra expense. A Weber is typically IME about double the cost of a similarly sized grill but built much much better. Again, IME, Weber’s tend to last 10-15 years (even kept outdoors and getting used 2-3 times per week) where other grills will last 2-3 years under similar circumstances.