That would be oil at the present moment...
But for the lucky one that gets past the oil people or those that control what energy source we harness next they will become more wealthy than the oil moguls.
We should be using HHO right now. with HHO you can run your gas powered internal combustion engine powered auto and only leave water as a bi product.
NO pollution, No scarcity, of course that mean that there would be No ability to control the market either. It is all about money.
That is why we do not have such a vehicle right now. But vehicles like this they do exist and they can be seen.
Just look up videos about Stan Meyers on Google. I think you would be surprised at what you see.