A vehicle capable of continuous operation in self-powered atmospheric, suborbital, orbital and space flight. As an added bonus I'd like it to be capable of deepwater high-pressure operation as well.
Then I'll retire to lounge atop the vast pile of treasure and wealth in the vault of my orbiting headquarters, only occasionally emerging to convey seemingly random and anonymous charitable donations in amounts that equal many small countries' gross domestic product.
A time machine/teleporter. But only I could use it. Then I'd go into the future and discover the secret to immortality. But only I could use it, until I found a way to market it to the world for an exceptionally high price.
I'd be the richest and most respected man in the world. Forever.
I would invent a machine that makes anything I want in just a few seconds. It makes the materials it needs for the things it's going to make out of air.
I would make it so everyone doesn't have to buy anything anymore. The only thing people still have to pay for is services and taxes.
Beat me to it, but I'll raise you, a one shot cure for every disease there is, was, and will be.
Touche.
I'd also like to invent a mini coffee maker. Not a flask to carry coffee around in, an actual cup sized maker that didn't need electricity that i could carry around. That would be great.
Since the medical domain has already been more or less covered, I'd invent the perpetuum mobile, a way to store (lightning) energy permanently and without significant loss, and the mobile self-sustaining biosphere. Just for fun I could also engineer a bacterium that excretes soda.
So many ideas have already been taken. So I guess I'd make a machine that makes muffins in just a second by pressing a button. Really can't think of anything that hasn't been thought of 100 times already.
