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?
I am willing to accept the absolute worst of humanity on the internet, because we can also have so many amazing things that weren't previously possible.
Accessibility of information to the masses is incredibly important. Isolated populations can learn about the bigger world, get help, and share their experiences. Friends and families can stay connected. People can work together from anywhere, and create value as a team in ways that weren't previously possible. When I was a kid it was just a dream, and now we are living it.
This is true, a lot of people, especially some people from older generations like to talk shit about the internet and modern age (not just social media), and it's effects on us which can be bad but that also depends on the person, with good moderation, internet really is a dream come true isn't it? And we are living it.
Something we shouldn't take for granted for sure in a way.