Radio is up there. Despite its bastardization under capitalist society, the ability to communicate instantaneously with people anywhere in the world with simple circuits, a modest amount of power and virtually zero infrastructure is remarkable.

It would help to narrow down context a bit, but I’m inclined to say the spear, because it was one of humankind’s main weapons for most of history and allowed us to avoid being constantly owned by big cats and other land predators. Alternatively, you could say the invention of clothing or coming up with reliable methods of starting fires.

As you can tell, I tend to interpret this question in a way that emphasizes early inventions for their role in helping us get “off the ground” in the first place, partly on the reasoning that those things were requisite for everything thereafter.

Pokemon’s Stun Seed

Reality. I’m not saying that because It’s a nice reference. Way I see it, inventions are a subset of reality. On an absolute level, reality is the greatest.

If we’re doing serious answers, the knife.