How about the transistor?
This tiny invention has played such an enormous role in technology and society as a whole. It has a solid silicon construction that prevents wear and tear. It translates electrical states into 1s and 0s. You can scale billions to fit into a microchip the size of a fingernail.
Modern versions switch trillions of times per second. It can be both a amplifier and a digital switch.
I could go on and on and on.
The transistor. Final answer.