Duke Nukem 3D
Duke Nukem 3D is a first-person shooter for DOS, produced by 3D Realms in 1996. The original game consisted of three episodes, L.A. Meltdown, Lunar Apocalypse, and Shrapnel City. The Plutonium Pak (which was thereafter included with the main release as "Atomic Edition") added a fourth episode, The Birth.
For more information, see the Duke Nukem Wiki.