Everyone should watch this one. It has way more stuff then the one I posted. 
 
-new perk is Mule Kick 
-gas zombies teleport short distances 
-spas-12 pick-up gives you the spas-12 (useless much......) 
-there's something about players getting infected and they attack you 
-wave gun get's split into two 
-Area 51 is a holding area (as stating in the achievements) and my guess is you face endless waves of zombies, without rounds, until you can get back to the moon via the teleporter 
-some sort of pyramid structure is shown, seems alien!!!! 
i believe wen u buy the mule kick perk, a random weapon powerup appears. i mean it makes perfect sense