Natural Selection 2 turned a year old yesterday, and it's on sale on Steam for 75% off in order to celebrate, which is $6.24 here in the States. The sale only lasts until November 4, so grab it while you can. The 24th patch for the game also went up yesterday, which just did some bug fixing and minor things.
If you have donated at least $75 to Natural Selection 2's Reinforcement Program, you will also get the the Shadow Gorge and Shadow Lerk, which look pretty cool. The Reinforcement Program is a way that you can choose to donate extra money to the game, and it lets Unknown Worlds release all of its new content and updates for free.