Let's see:
There are throat microphones . These microphones pick up sound directly from the throat, not the mouth. The sound is much clearer, and the microphone picks up only the sound of your voice, and nothing else.
Why didn't they replace the previous, less efficient pickups? Because they are different from what people are familiar with. We often prefer the solution we are accustomed to over the more effective one.
It's possible to find some, but not in stores.
Then there's the Dyson washing machine.
Yes, Dyson did make a washing machine. This machine had two cylinders that rotated in opposite directions.
Dyson engineers discovered that hand-washing clothes for 15 minutes removes more dirt than an hour of washing in a conventional machine.
Their machine simulates hand washing. Again, the product was very different. People also feared that the counter-movements would damage clothes and, more importantly, as these were early models and Dyson products, they were very expensive. They never reached the stage of economies of scale.
Google Glass
These glasses enabled augmented reality, internet connectivity via voice command, an integrated camera, etc. They worked very well, so well that they violated several privacy laws.
Astropaths of Lululemon
Yoga pants for women. They were very comfortable, but also very thin. And they became almost see-through when the fabric was stretched, like when you do a stretch, like… during a yoga session. I'm not going to post a picture.
And finally, HD DVD.
HD DVD was a competing format with Blu-ray . There was no perceptible difference. The two products were the same. But people liked the name "Blu-ray," and the Playstation 3 console had built-in Blu-ray. PS3 owners were therefore buying Blu-rays. Toshiba, therefore, abandoned a very expensive format war.
(Blu-rays had more space, at most 20 GB more. On the other hand, no film at the time, or that I know of today, could reach that limit (50 GB). Layers could be added to both formats, and Toshiba created a 50 GB disc in 2007. For these reasons, storage space was not relevant in the context of the format war.)
Honorable Mention: Beta Tapes.
There are also several flavors that have been discontinued due to poor sales. In this case, we changed the packaging and increased the price.