What is the greatest hardware innovation for video games?

From the directional pad designed by Gunpei Yokoi for Donkey Kong, to cartridges with built-in batteries to allow saving which was first introduced with The Legend of Zelda, to motion control which was explored with the NES Zapper and became popular with the game Duck Hunt and would later be re-explored in the Wii remote and the Switch Joy-Cons, to optical media for larger storage capacity, to VR headsets which add more depth and immersion to video games, to many more innovations out there, which hardware innovation do think is the greatest or most influential and why?