Upgrading the Atomwaffe makes the weapon doubles the shoot per mags, improve reload time and allow reviving downed mate by shoot them.
To begin the upgrade, shoot the 3 tank on the crafting table of the Atomwaffe.
Next you will need to throw a grenade on a rock outside the map and gather the stone by shooting the keeper 3 times.
Go back to the crafting table
You can now get your upgraded Atomwaffe for 5000 points
To unlock the secret room near Mule Kick, that contains Kunjora's Battle Mace and the Gobble gum dispenser, you will need to put 1000 points to a checkout at the 3 entrance of the mines.
Vigor Rush entrance, from spawn
Double Tap entrance, from Spawn
Juggernog entrance, from Main Place
To get a free perk and extra perk slot, you need to get the Bowie and cut 3 capsule held by a zombie hand around the map.
Once done, a ghost keeper will give you the free perk by the Juggernog side of the mines.
Next to the Bowie knife, at the Main Place
At the mines, between the 2 tunnels of Spawn
At the Juggernog sides of the mines.
To get the Madgaz's special Ray Gun MKII, you will first need to get the regular Ray Gun MKII. You have a small chance (much higher than the fuse Ray Gun from Der Eisendrache) to get it by throwing a coin inside the rail system.
Ray Gun MKII from the rail system
Pack-A-Punch the Ray Gun MKII
You now have a yellow full-auto Ray Gun MKII.