...especially if you're a Half-Life fan.Apparently someone disliked how Valve did HL:S so they re-wrote it into Black Mesa: Source(Now just Black Mesa). It looks interesting, I'm not a big fan of the HL series, and it's got me interested. There's not much there yet, but in time, they should have the game done. One particularly nice aspect about it: It's free. I'm all for free games like this, man(case in point: My current favourite FPS is a free multi-player extension of Return to Castle Wolfenstein).
I'm definitely keeping an eye on this for the release.