Doom

Doom, a first-person shooter released in 1993 by Id Software, is lauded for its intense 3D graphics and multiplayer networking. The objective: make your way to the next area while avoiding (or significantly harming) all the opponents in your way.

Within two years, the game--distributed as shareware--was downloaded by an estimated 10 million people, according to Wikipedia. Its interactive violence has incited debate about warning labels and parental control.