Half-Life: Opposing Force

To use codes, you have to run the game with the console enabled.
Launch Half-Life in developer mode by going to your Windows Start menu, selecting "Run", and typing 

C:\Sierra\Half-Life\hl.exe -dev -console -game gearbox 

During play, press ~ to bring down the console.
Now enter one of the following and press Enter to activate:

Code				Effect
-----------------------------------------
impulse 101         All weapons and ammmo   
/god                God mode  
/noclip             No clipping  
/map XXXXXX         Map select.
/give weapon_XXXXX  Spawn weapon.
/give ammo_XXXXX    Spawn ammo.
/give item XXXXX    Spawn item.
sv_gravity XXXXX    Adjust gravity.
-----------------------------------------
  

Map names:
of0a0
of1a1
of1a2
of1a3
of1a4
of1a4b
of1a5
of1a5b
of2a1
of2a1b
of2a2
of2a3
of2a4
of2a5
of2a5b
of3a1
of3a1b
of3a2
of3a3
of3a4
of3a5
of3a6
of4a1
of4a2
of4a3
of4a4
of4a5
of5a1
of5a2
of5a3
of5a4
of6a1
of6a2
of6a3
of6a4
of6a4b
of6a5
of7a0 

Weapon names:
displacer
eagle
grapple
knife
m249
pipewrench
shockrifle
sniperrifle
sporelauncher
Assault Rifle 9mmar  
9mmhandgun  
crossbow 
crowbar  
egon 
gauss
handgrenade  
hornetgun  
knife 
tripmine  
rpg  
satchel    
shotgun 
snark 
sporelauncher

Ammo Names:
357 
Rifle 9mm  
9mm 
crossbow 
egonclip 
gaussclip  
556 
762  
rpgclip  
buckshot 
spore