Half-Life: Opposing Force

Cheat mode:
Load game with the hl.exe -dev -console -game gearbox command line. Press ~ during game play and enter one of the following console commands to activate the corresponding cheat function.

Effect	Code
All weapons and ammunition	impulse 101
God mode	/god
No clipping and flight modes	/noclip
Level select	/map <map name>
Spawn indicated item	/give <item name>
Spawn indicated weapon	/give weapon_<weapon name>
Spawn indicated ammo	/give ammo_<ammo name>
Auto-reload enabled	+reload
Auto-reload disabled	-reload
Adjust gravity	sv_gravity <-999 - 999999>

Some mobyjr, Chris Walker, and Victor Chan.

Weapon	Weapon name
.357 Magnum	357
9mm Assault Rifle	9mmar
9mm Handgun	9mmhandgun
Crossbow	crossbow
Crowbar	crowbar
Desert Eagle	eagle
Displacer	displacer
Egon Gun	egon
Gauss Gun	gauss
Grapple	grapple
Hand Granate	handgrenade
Hornet Gun	hornetgun
Knife	knife
Laser Tripmine	tripmine
M249 SAW	m249
M40A Sniper Rifle	sniperrifle
Penguin Bomb	penguin
Pipewrench	pipewrench
Rocket Thrower	rpg
Satchel Charge	satchel
Shock Rifle	shockrifle
Shotgun	shotgun
Snark	snark
Spore Launcher	sporelauncher

SegaGenesisFrek.

Ammo type	Ammo name
.357 Magnum	357
9mm Assault Rifle	9mm
9mm Handgun	9mm
Crossbow	crossbow
Egon Gun	egonclip
Gauss Gun	gaussclip
M249 SAW	556
M40A Sniper Rifle	762
Rocket Thrower	rpgclip
Shotgun	buckshot
Spore Launcher	spore

monster_otis (Otis)
monster_human_torch_ally (Engineer)
monster_human_medic_ally (Medic)
monster_human_grunt_ally (Grunt with no weapons)

Boot Camp:
ofbooto
ofboot1
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ofboot4

Regular game:
of0a0
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of1a5
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of2a1
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of2a2
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of2a4
of2a5
of2a5b
of3a1
of3a1b
of3a2
of3a3
of3a4
of3a5
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of4a1
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Hidden audio:
Approach the Boss of Opposing Force to hear backwards audio composed of the phrase "To win the game you must kill me Randy Pitchford" when played correctly. Randy Pitchford is the leader of the development team at Gearbox Software.

Hint: Get a gun at the beginning of the level:
At the beginning of the level where you reach the security guard, find a chair. It is easily moved. Move it to the door that he will open for you, and get him to open it. Slide the chair in between the doors, and it will not close. This may take a few tries. Go out, take the crowbar, charge it up until you reach the same security guard, and hit him until he explodes. Then, get his pistol with the laser sight and continue the game.
Vincent Siu.

Hint: Hidden health:
When you are about to finish the "package" and are near to going into "Worlds Collide", use the Trans Locator's secondary trigger (which will teleport you into Xen). You will end up in a small cave overlooking a massive healing pool with two Bullsquids also wanting to enter it. To kill them quickly, shoot them with the Desert Eagle. To resume the game, run through the cave until you find a Teleporter Ball.
lilly smith.

Hint: Spawn Grunts:
Enable cheat mode, then use the impulse 76 code to activate the Grunt-O-Matic. A message to start a new game in order for it to work will appear. If you want to continue where you currently are, just quicksave, then quickload the game. Once you have quickloaded, type in the code again to spawn a Grunt. Note: You must have the /noclip code on before you spawn the grunt because he will be spawned close to you. If this is not done, a message stating that the monster spawned is stuck in a wall may appear and the game will end. Do not spawn the Grunt in a closed position or the same message will appear. The Grunt you spawn will see you as a hostile. To have more fun, use the /notarget code and spawn a number of grunts to do your alien hunting. The Grunts you spawn will look like the Grunts from the original Half-Life.
Justin Pickul.

Hint: Fun with spawning:
Enable cheat mode, then use the entities code to get a list of the creatures in the location you are currently in. Usually, when you try to spawn a creature, you have to use the noclip code to levitate in the air and spawn the creature nowhere near any objects. If a part of a spawned creature is spawned within a wall, ceiling, or another creature, the game crashes. However, if you enable the developer 0 code, the game continues even if a spawned creature is stuck, but the creature has yellow dots around it. Also, bind the spawn commands to unused keyboard keys; for example bind X "impulse 76" or bind y "give monster_scientist". The impluse 76 code works everywhere, and the hostile grunts created with it are easy to place where you want them; as they appear in front of you, rather than above. Now, enable the noclip code and fly around pressing the bound keys. Watch as Barney's Aliens and Grunts battle it out while Scientists run around being slaughtered.
xander77.

Hint: Set health or damage values of player weapons and enemies in single player mode:
Type sk_ at the console window and repeatedly press [Tab] to cycle through the values. The sk_plr_ values are for the player's weapons, while other values are for enemies and health/shield chargers. The 1, 2, and 3 at the end of the syntax corresponds to the difficulty settings easy, normal, and hard. Set their values accordingly. Enter a number, a space after the syntax, then type restart to confirm the changes. For example, sk_plr_rpg1 99999 makes the rocket launcher in easy mode inflict 99999 damage with a blast radius that wipes out everything in the level.
Yuan Tien.

Hint: Killing Gordon Freeman:
Go to the map named "of3a1". This is the map where you see Freeman running into the teleporter. Follow him into that same teleporter. After the map is done loading, you will see yourself falling. Normally, if you let yourself fall the game will restart at map "of3a1". However, if you enable the /noclip and go to the nearest platform in front of you, Gordon Freeman will appear. Gordon just stands there with no weapons, and wears silver sunglasses. It takes some time to kill him with just bullets -- try grenades or a very powerful weapon. Alternately, you can go to this location enabling the map of3a1b code.
lhrsSecret Agent.

Hint: See Shepard:
Successfully complete the game and wait until the credits are over. After the screen turns black, enable the brightness 9999999999999 code to see Shepard.
auer.

Hint: Redo the sniper course:
During boot camp, shoot the trainer and you will start again at the beginning of the course.
m23333.

Hint: Give any gun the magnification of a sniper rifle:
Save with the gun you want to be magnified. Then, switch to the sniper rifle and turn on the scope. While the scope is on, load the previous save.
Lowfatspred25.

Hint: Vortigaunts on the Hazard Course:
After getting the Displacer on Xen, use the secondary fire before you go through the portal to Earth. You will be warped to the Crouch-Jump section of the Hazard Course, where one Vortigaunt will attack the holographic instructor. On the other side of the room is a second Vortigaunt and a shotgun. The portal exit is in a corner of the observation room.
Galak Fyyar.

Hint: Hidden programmer message:
At the end of the game while G-man is talking to you in the helicopter, enable the chase_active 1 code to go into third person view. Then, look up through the roof of the helicopter. Printed on the sky will be a hidden programmer message which reads, "Hack hack hack, all day long. Hack hack hack, while a sing this song." (referring to the fact that you will be currently cheating at this moment).
Laytz94.

Hint: Valve reference:
Enable the brightness 9999999999999 code and go to map of3a4. After the part where you save the scientist in the clean suit and he lets you through the first locked door, there will be a room with three fish tanks. The middle one will be cracked open. Climb up through it and into the dark crawlspace with all the Xen monsters in it. On the walls will be the Valve corporation printing.
Laytz94.

Hint: Valve, Steam, and Gearbox references:
Go to map of4a4. This is the map with the Pit Worm. Notice that in order to flush the radioactive waste, which kills the worm, you must first complete several tasks. These include opening the Steam vents, the Valves, and activating the Gearbox. These are the names of the major corporations which created the game.
Laytz94.