Get out of 'Nacht Der Untoten' map
Go into the 'Help room' and look around. Get a gun that lasts it's ammo for a long time and walk up to the boxes near the zombie barricade round the corner of the help door and run into the little space between them that you can't fit through. The game will lag for a bit then while it lags put the charger in.
To get the flamethrower first get 3000 points or more. Once you have all of the money remove the baricade to get up stars. Now you have 2000 points (or more). Go forward into this big room. turn right and you will see some fire. go to the fire. There will also be a new gun. Turn around to see a red cabinet open it for 2000 points to get it.
use only your knife thru level two then between level two and three get the mystery box and you will get the ray gun.