Hexen II: Hammer of Thyrion (a.k.a. uHexen2) is a free and open-source 3D first-person-shooter (FPS) game. The Hammer of Thyrion is a port of the classic Hexen II and HexenWorld, originally developed by Raven Software. There have been may graphical enhancements from the original with OpenGL such as: multitexturing, glow effects, anisotropic texture filtering, lighting enhancements and more.
Mac OS X 10.6 Snow Leopard or newer
OpenGL graphics card
Free download at sourceforge.net