Mouse
Pointing device for computers. Douglas Engelbart invented it in 1964, demonstrated 1968 ("Mother of All Demos"). Wooden box with two wheels, signals for X and Y movement.
Engelbart never got royalties (the patent expired before PCs went mainstream). Xerox PARC picked up the idea, Apple Lisa (1983) + Macintosh (1984) made it famous. Mechanical roller-ball (rubber ball) → optical (LED + sensor, 1999) → laser (more precise, works on more surfaces). Trackpoint, touchpad, trackball are alternatives. Gaming mouse market: Logitech, Razer, SteelSeries.