I don’t know if it’s the most useless thing ever, but I got an electric corkscrew once as a present, like this one. Yes, it works, but not any better, faster or cleaner than any mechanical corkscrew does. And it’s big and bulky, and I drink wine so rarely that any time I have to open a bottle the battery would be drained, because I sure don’t leave that god ugly thing permanently at its charger.
Is the War on Drugs too conceptual, or are we meant to stick to things like the banana slicer? If it’s allowed, I’ll vote the War on Drugs. If not, I’ll say… the BAND The War On Drugs.
I know, right?
As an aside, the George Foreman grill, though sold on TV, is a very handy item that’s gotten a lot of use in our house.
Yeah, even though I open a lot of wine bottles, this gadget has no use. I was given one as a gift and probably used it twice.
Locking your keys in the car. Used to do it every two months or so, until I got a car with a key fob. So, this is definitely a win for me, but I can understand people who are actually competent at things not seeing the point.
My uncle gave me a wine aerator once.
Cell phones used to be much more useful, but now they’re smaller and lighter and wouldn’t aren’t nearly as good for holding down papers in a strong wind.
Dear god, yes! I miss Usenet. 
Can you imagine a world with gigabit speeds and no pointless companies like Facebook, Instagram, Snapchat, and Twitter?? And all the unwashed masses are off the interwebs because connecting is more complex than mashing a giant rounded-corner square icon with their grubby oversized fingers? It would literally be internet heaven!
You’re a real visionary. I hope somebody become the next Jobs with this “hard internet” idea (in all seriousness). 
Here’s one of a few similar products that people sometimes pick up, thinking that they will be useful.
Useless, and worse than useless, because dog owners think that they are actually doing something useful, when they are really just doing extreme damage to their dog’s hair.
Fortunately, most are not so gullible to believe the advertising, but I do have clients come in with dog’s fur matted to the skin and above the matting is just completely ragged and ruined fur. Then they are upset that I tell them how bad a shape their dog is in, and that we are probably going to need to shave down and start over.
They say, “But I was brushing, I even got an electric detangler!” :smack::smack::smack:
I keep mine in my pocket so I never get locked out of my car.
RLS is a disorder that can compromise marriages and overall health, by waking people up dozens of times a night. However, I do understand where you’re coming from; when lesser measures like mild sedatives fail, they use Parkinson’s meds, and some of those are almost worse than the disease.
How about the Veg-O-Matic and its knockoffs? It takes longer to assemble, clean, disassemble, put away, etc. than the time saved by getting out a knife or grater and doing it by hand.
Obviously the above was written by someone who’s never experienced RLS. It’s hell. Posters here have written threads on it and how awful it is. The name of it sounds quaintly innocuous, but it’s not. Look it up.
Could this also be described as an electric dog polisher?
Very first world attitude. The cell phone allowed billions of people to leap over the issue of running land lines to their house. Now that cell phones have data access, it provides the same utility as computers. Farmers can check and see what their products are actually worth, not rely on the word of a middleman. Merchants know the correct, up to date exchange rates. Third word students have access to more information than first world students did 30 years ago in big-city libraries.
To me, the most useless thing is Twitter. Followed closely by the avocado slicer. https://www.amazon.com/OXO-Good-Grips-Avocado-Slicer/dp/B0088LR592
actually i have a set, my husband will make me up some hard boiled eggs within because chemo has given me neuropathy in my hands that has both killed my hand strength and dexterity, i can’t manage the fine motor control to peel a damned egg without trashing it, so it is perfect for me.
Like with many accessibility adaptive items, unless you need them you would consider them useless. Normally I would consider those sock aidsuseless, but I can see how if you are flexibility impaired they would be useful. [or very pregnant, I can remember a friend of mine rolling around on her bed twisting to get socks on and pulled up.]
Most of the developing world didn’t have either. Now they have mobile phones, and it’s made a real, positivedifference to them.
The opinion expressed in the OP is a dumb parochial one showing limited insight or awareness of the global impact of the tech in question.
Only a lot of the long-distance ones. But not the Russian scams (those don’t come from Russia’s remote areas), or all those pyramid scams for which the US is famous, or heck, any of the classics.
That I can use my phone to help me navigate a foreign country’s roads, and my hotel can send me a SMS because they’re worried I’ve been caught in the blizzard and I can stop whenever it’s convenient to check it? That’s as big a communications revolution as writing was.
Extraneous apostrophes. I don’t remember seeing so many except in the past 50 years. Totally useless.
It’s not useless, just a tip of the hat to the time in history when “cat” was a foreign word that English-speakers weren’t sure how to pluralize, like writing Viszla’s instead of Viszlak. 
That’s because third word students were hungry for information, angry that they couldn’t get it, and I forget what else they were, but I’m sure I can use my smartphone to find out the third word.
I wouldn’t call cell phones “useless,” but I’d submit they have brought great harm along with their supposed benefits.