Cube 2 Sauerbraten is a free first-person shooter game thats built as a major redesign of the Cube FPS. The game can be played as single player and multiplayer. The gameplay is very oldschool and fast paced (Doom & Quake 1 like), has many multiplayer gameplay modes, 2 single player modes and 7 weapons to choose from.
Mac OS X 10.4 or higher
Intel powered Mac
OpenGL 2.0 compliant graphics
Free download at sauerbraten.org