rott (Rise of the Triad, first person shooter game)

Rise of the Triad is a high quality, fast scrolling first-person
perspective 3D action game. It includes a lot of destructive enemies,
an arsenal of weapons from simple pistols to missile launchers,
life-preserving armor, traps and ambushes galore.

WARNING: Rise of the Triad features wanton and gratuitous violence.

In order to play the game, you need the data files from either the
retail or shareware (demo) version of the game.  The shareware/demo
data files are included in the package. If you want to play the retail
version, see README_gamedata.txt for details.

Multiplayer games (aka comm-bat) are NOT truly supported: you can
start up a comm-bat game, but you can only play by yourself (no actual
networking code exists in this version of the game).

For more information, see http://www.3drealms.com/rott/