Duke Nukem Forever is part four in a series of PC games featuring Duke Nukem as the hero. Parts one (Duke Nukem) and two (Duke Nukem 2) were sidescrollers/platform games, and part three, Duke Nukem 3D, was an FPS. Duke Nukem 3D became one of the top-selling games of all time, and is a very important part of FPS gaming history; it is one of the few "legendary" titles, together with Quake and Doom. The game is one of the most sophisticated FPS games ever. It features everything the Unreal engine has, but also features things like LOD, skeletal animation, and motion capture, for an optimal playing experience.
DooM Legacy is an enhanced port of Doom, the classic first-person shooter from iD Software. It features high screen resolutions, an OpenGL renderer, fullscreen modes under X, client-server architecture for up to 32 players on IP-networks, Quake-style keybindings, a console, and more. It is available for Linux, DOS, and Win32.
Vavoom is a DOOM source port incorporating Doom, Heretic, Hexen, and a little bit of Quake. It runs on DOS, Windows, and Linux and includes many advanced features like OpenGL and Direct3D support, translucency, freelook, jumping, a client/server architecture with in-game joining, a Quake-style console, a powerful language to describe game logic (Vavoom C), and much more.
UProxy is a proxy for UDP protocols. UProxy was initially designed to allow users to play Unreal Tournament matches over the Internet on computers sharing a dial up connection. It could also be used by any client-server application that uses the UDP protocol and doesn't require clients to bind a fixed port. UProxy should run under Windows, Linux, or any OS which supports BSD sockets.
Warsow is a standalone, eSports-oriented FPS game. It is based on Qfusion, an advanced modification of the Quake 2 engine. It features fast-paced gameplay focused on trix (trick jumps) and art of movement. War§ow features a complete power-up system, including weak and strong fire mode for each weapon in all "normal" gametypes as well as Warshell (battle shield) and Warshock (quad damage) for team-based gametypes. Its cartoonish graphics use cel shading with a style that is similar but not identical to Manga.
The Castle is a first-person shooter game in a dark fantasy setting. Your main weapon is a sword, so the fight is mostly short-range. Three main levels are included, packed with creatures, items, and sounds. A couple of bonus levels are also available, like the classic DOOM E1M1 level reimplemented in VRML. The game engine is based on VRML, OpenGL, OpenAL, and all shadows are done by the shadow volumes approach.
Sauerbraten (a.k.a. Cube 2) is a free multiplayer/single player first person shooter, built as a major redesign of the Cube FPS. Much like the original Cube, the aim of this game is not necessarily to produce the most features and eye candy possible, but rather to allow map/geometry editing to be done dynamically in-game, to create fun gameplay and an elegant engine.