AssaultCube is a FREE, multiplayer, first-person shooter game.
Eureka is a DOOM map editor
Open source FPS/RTS Game
3D-Accelerated open-source DOOM engine
Historically accurate Doom source port
A ZDoom Frontend
FreeCS is a free-software reimplementation of Counter-Strike 1.5.
EDGE is an advanced DOOM source port
Source port of Doom, Heretic, Hexen and Strife developed in Delphi
A fun realistic multiplayer free-and-open-source first-person-shooter!
Doom (Shareware) Installer for Windows x64 platforms.