Today's daily deal on Steam is a four-player shooter by the name of Revelations 2012. It seems cheap, reduced from $9.99 to a mere $4.99, but I've played it. I played it to review it, and the review is going up tomorrow. Until then, I can but warn you, urge you, plead with you to ignore it.
Even at free, this poorly made Left 4 Dead mod would be asking too much.
It disgusts me that tripe like this gets approved ahead of Mutant Mudds, seemingly just because it uses the Source Engine. That's the way of the world though. In any case, you really should keep away from it and get something else. Like, say, Zeno Clash or something.