General sound made by bouncing things.
Also, a legendary Amiga demo, written in 1985.
It was a "demo" in a sense that it was a display hack, and also a "demo" in a sense that it was supposed to be a demonstration of Amiga capabilities.
According to the legends, the demo was written in one night by R. J. Mical and Dale Luck. The demo displays a red-white checkered ball that bounces around the screen. People who saw the demo didn't even believe the ball was drawn by Amiga, and looked around for hidden VCRs...
These days, the ball is the official logo of Amiga. The demo is still floating around the world, and comes with Amiga Forever package. An OpenGL "replica" also exists, for the PC crowd.
See: boing ball