Start the game with the commandline parameter '+set sv_cheats 1'. Then during gameplay,
 press [~] to bring down the console. Now type any of the following codes:

 /god                      God mode
 /notarget                 Invisibility
 /noclip                   No clipping mode
 /give all                 All weapons and ammo
 /give armor               Give armor
 /give health              Give health
 /give stamina             Give stamina
 /give ammo                Give ammo
 /give #                   Give item # where # might be
                           panzerfaust
                           thompson
                           mp42
                           mauser rifle
                           flamethrower
                           sten
                           fg42 paratroop rifle
                           grenade
                           colt 45
                           large health
                           medium health
                           knife
 /mapname                  Get the current map name (use in next cheat)
 /spdevmap mapname         Jump to mapname, where mapname might be
                           escape1
                           escape2
                           tram
                           village1
                           village2
                           crypt1
                           crypt2
                           church
                           boss1
                           forest
                           rocket
                           dam
                           chateau
                           dark
                           dig
                           castle
                           end
                           beach
                           village
                           boss2
                           rocket
                           baseout
                           assault
                           mactory
                           trainyard
                           norway
                           xlabs
                           wine
                           wine2
                           wine3

                           or type
 /dir maps                 List all maps
 /kill                     Suicide
 /cg_uselessnostalgia 1    Original Wolfenstein interface
 /nofatigue                Unlimited stamina
 /quit                     Exit game
 /toggle cg_drawtimer      Show time left
 /cmdhist                  See all commands
 /serverinfo               See server settings
 /reconnect                Reconnect to server
 /toggle r_fullscreen      Toggles windowed and fullscreen and restarts
 /toggle cg_draw2d         Show hud
 /cg_FOV [number]          Change field of View
 /toggle cg_gibs           Gibs toggled
 /toggle cg_drawteamoverlay    Team overlay toggled
 /toggle cg_drawcompass    Compass toggle

 You can only start this game in cheat mode if allready load a map in cheat mode. So if
 you want to start at the beginning load the 1st map with

 /spdevmap escape1

 and then you can play in cheat mode.

 Alternate method to start the cheats:

 1. Add " +set sv_cheats 1" to the target line of the shortcut, as shown above.
 2. Add a blank "user.cfg" file to the folder labeled "Main", in the game folder.
 3. Type one line in that "user.cfg" file: set sv_cheats 1
 4. Enter codes as shown above.