Epic Games now offers downloads of a playable pre-alpha build of their Unreal Tournament revival for registered users of their forums (thanks BeyondUnreal). They go to great lengths to stress this is a preliminary release fraught with bugs and placeholders, and that it is intended to inspired feedback from those interested in helping shape the multiplayer first-person shooter. The Unreal Tournament website explains:

The forum post describing how to install the UT pre-alpha playable build is only visible to signed in forum members in the Top Secret Members Only forum. Unreal Tournament is still very early in development, so the build is incomplete, buggy, full of placeholder art and therefore is not in any way representative of the ultimate vision for the game. You really shouldn't play it now! We’ve made it available to Unreal Tournament forum members so they can try the game out and offer constructive feedback on these forums, or maybe even jump in and start contributing.