What are some alternatives?
When comparing OpenArena and Urban Terror, you can also consider the following products
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Quake - Quake is a series of first-person shooter video games released by id Software.
Unreal Tournament - Unreal is a series of first-person shooter video games developed by Epic Games.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Red Eclipse - Red Eclipse is a fun-filled new take on the first person arena shooter, built as a total conversion...
AssaultCube - AssaultCube is a FREE multiplayer first-person shooter game. Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun!