After reading the various answers to the question, I'm going to sneak through the door opened by Philip Anderson and nominate a discovery instead of an invention. And it is the Copernican Theory. Generally it was a counter-intuitive idea, and it ran opposite to the interpretation of senses (not to mention the Church) I mean, one could "see" the sun going across the sky. What could be more obvious than that? A nice move. It took a lot of intellectual courage, and taught us more than just what it said.