Perks are items that help players in Nazi Zombies. They cost points and are lost if you get downed, but they can be a big help in-game.
A perk that increases your resistance against zombies, so you can take more hits from a zombie before getting downed. In Der Riese, the Juggernog machine can be found on the second floor past the Bouncing Betties. It costs 2500 points.
Double Tap Root Beer
Double Tap decreases the delay between bullets. In Der Riese, it can be found past the bridge towards Teleporter B. It costs 2000 points.
Speed Cola decreases the time it takes to reload a gun. It is best for guns with large ammo capacity like the MG42 and the Browning M1919. Speed Cola is the most expensive perk at 3000 points. In Der Riese, the machine is placed next to the FG42.
A perk that decreases the time it takes to revive another player. In Der Riese, it's placed towards Teleporter C. Quick Revive is the cheapest perk, at 1500 points.