You call can troll me, call me names, or whatever but this is what is. When you play the game make sure you remember to thank me. WARNING! THERE ARE MANY SPOILERS! I will put this (*) symbol around big spoilers. The more stars I put around it, the more of a big spoiler it is. So here we go:
The Wave Gun: You shoot it at a crowd of zombies, and they literally puff up and explode. But that's not all this gun does. By pressing left on the d-pad, you can literally split the gun in half, resulting in two separate handheld guns, titled the Voltage Rays. You hold them one in each hand, and they shoot electricity, similar to the Wunderwaffe DG-2, however the Voltage Rays zap less zombies with each shot.
**Another thing I want to tell you about is the new special grenade, the Quantam Entanglement Device. When you throw it, it creates a large, dome-shaped force field around it which zombies are seemingly magnetically pulled into, and everything you do to one zombie in the force field happens to all the others in it. For example, if you shoot one zombie, all the others will have a bullet hole in them as well**
****Another thing you might be interested in knowing about is the new perk, Three-Gun Tequila. As you can probably guess from the title, this perk allows you to wield three weapons instead of the regular two. It costs 3,000 points to buy, its color is grey, and it symbol is a pistol with two phasing pistols stacked under it. If you get downed with this perk, you lose the weapon you were currently holding, but if you're revived and you buy the perk again, you get that weapon back****
It may also be worth mentioning that you cannot leave the base for more than fifteen seconds seconds if you don't buy a space suit, which can be bought in multiple locations around the map for 1,000 points. When you die, you lose yours.
******The last thing I'd like to mention is how you access the Pack-A-Punch machine on Moon. In the power room, there is a large teleporter. To turn it on, you must activate ten different switches scattered around the map. Once you do that, the teleporter turns on for thirty seconds. If you can make it there and teleport, you will end up in Area 51. Here there is a fairly wide open area with the Pack-A-Punch machine in the center. After a minute, you will be teleported back to the moon.******
I also know about the the phasing zombies but I'm gonna let that me a surprise for you. ;)