As a car enthusiast, I can think of a good one, the Ford Nucleon.
During the 1950s and 1960s, there was considerable interest in nuclear power and its potential applications. This led to the idea of using nuclear energy to propel cars. The concept behind a nuclear car was to utilize a small nuclear reactor to generate steam, which would then power the vehicle's engine.
Of course back in those days, this was extremely futurustic and some at the time thought this would be a game changer, but ultimately, the safety aspect was one of the biggest reasons why this idea was dropped, and I probably don't have to explain why it may not have considered to be safe, I mean, it was using nuclear power, so even if the engineers tried to make it as safe as possible, IF something went wrong, it would have been catastrophic.
Ever since then, the interests in the automotive sector has shifted to Electric and Hydrogen.
Still, a very intriguing concept car and idea.
Outside cars, you have blimps, and I personally believe if we tried to make something like a hindenburg today with existing technology, we might have been a lot more successful than back then (as it goes way back to 1930s), there are still some blimps used occasionally, I also don't believe those use hydrogen(?), but they are not the "game changer in air travel" it was once seen as, although we can't rule out a comeback.
What about you guys?
VR is probably the biggest I’ve seen it already. I got my son a Valve Index about 2 years ago now and it’s still seeing frequent use. There’s quite alot of games out there already. As interested as I was for Apple’s glasses, I’m not sure that it’s going to cause a big revolution in AR/VR. Maybe, it could, but their promo for it was a bit weird and the price seems crazy high for now.
I think the big hold up are the games. The good games require an expensive PC, expensive headset, and a dedicated space. They can't get returns for big budgets until headsets are common and people wont dump big money unless they think its worth. The only option is the slow burn. It's a lot of fun but selection is a bit dull once you burn though the big names.