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:SierraHalf-Lifehl.exe -dev -toconsole
Now load the last quick saved game (F6), then press the ~ key to pull down the console. Type in sv_cheats 1 and press Enter. Cheats are now enabled, but you need to die or reload your game before you can use them.
Now during play, press the ~ key and type in the following codes:
/god - God mode on/off
/notarget- Enemies ignore you
/impulse 101- All weapons and ammo
/impulse 102- Spawns giblets and blood
/impulse 103- Shows monster stats while looking at monster
/impulse 104- List global entities
/impulse 105- Silent Player
/impulse 106- Model/sprite stats, while looking at target
/impulse 107- Texture name, while looking at object
/impulse 195- AI mode on
/impulse 203- Delete monster or NPC from world
/thirdperson- Third person view
/firstperson- Return to first person view
/noclip - No Clipping (Walk Through Walls, Etc.)
/map C#A# - Go to any map (enter numbers for #: C1A1, C1A2, Etc.)
developer 1 - Developer mode on
developer 2 - Verbose developer mode
developer 0 - Developer mode off
/give XXXX - Gives any item. In place of "XXXX", enter one of the following:
item_airtank
item_antidote
item_battery
item_healthkit
item_longjump
item_security
item_sodacan
item_suit
ammo_357
ammo_9mmar
ammo_9mmbox
ammo_9mmclip
ammo_argrenades
ammo_buckshot
ammo_crossbow
ammo_egonclip
ammo_gaussclip
ammo_glockclip
ammo_mp5clip
ammo_mp5grenades
ammo_rpgclip
weapon_357
weapon_9mmar
weapon_9mmhandgun
weapon_crossbow
weapon_crowbar
weapon_egon
weapon_gauss
weapon_glock
weapon_handgrenade
weapon_hornetgun
weapon_mp5
weapon_python
weapon_rpg
weapon_satchel
weapon_shotgun
weapon_snark
weapon_tripmine
