Half-Life

Cheat mode:
Load game with the command line: hl.exe -dev -toconsole. Then, press ~ if the orange text on the screen does not disappear. During gameplay, press ~ to display the text prompt and type in sv_cheats 1. Press ~ and enter one of the following console commands to activate the corresponding cheat function.
Pongo Pigmeus.

Effect	Code
God mode	/god
Adjust gravity	/sv_gravity <-999 - 999999>
All weapons and ammo	/impulse 101
Developer mode on	/developer 1
Verbose developer mode	/developer 2
Developer mode off	/developer 0
Suicide	/kill
Map select1	/map <map name>
No clipping mode	/noclip
Obtain item2	/give <item name>
Opponents ignore character	/notarget
Third person view	/thirdperson
Return to first person view	/firstperson
Auto-reload enabled	/+reload
Auto-reload disabled	/-reload
Set reload speed; 0 is fastest, 3500 is default	/rate <0-3500>
Speak word	/speak <word>
Speak sentence	/speak <word.word2.word3>
See things brightly without flashlight	/lambert -1.0001
Toggle light amplifier	/r_fullbright <0,1>
Strange colors and wireframes	/r_fullbright 9
Toggle game speed	/host_framerate <0,1>
Spawn human grunt	/impulse 76
HEV suit, weapons, and ammo	/impulse 101
Spawns gibs and blood	/impulse 102
Monster stats, while looking at monster	/impulse 103
List global entities	/impulse 104
Silent player	/impulse 105
Model/sprite stats, while looking at target	/impulse 106
Texture name, while looking at object	/impulse 107
Control onscreen monsters	/impulse 109
AI node information	/impulse 195
AI node information	/impulse 196
AI node information	/impulse 197
AI node information	/impulse 199
Spawn blood	/impulse 202
Delete monster or NPC from world	/impulse 203

1. Select a map name from the following list.
2. Select an item name from the following list.

Ed Bradley, Delane Fazio, mobyjr, Chris Walker, Quinn, Spyder, Victor Chan, Leprachaunjohn, Poohead900, Kyle, Dan 42, joe becker, 01lawreyanstis, inferno bat and others.

Single player
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Multiplayer/Deathmatch
boot_camp
bounce
datacore
lambda_bunker
snark_pit
stalkyard
subtransit
undertow

Hazard course
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Item name list:

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
weapon_quantumdestabilizer

Effect	Command line parameter
Press ~ during game play to activate console	-console
Alternate latency display in v1.0.0.8 or later	-numericping
Bypass opening FMV sequences	-nointro
Disable dial up networking box during LAN play.	-noip
Disable DirectSound	-wavonly
Disable IPX errors during LAN play	-noipx
Enable developers mode	-dev
Force amount of RAM available to game	-heapsize <bytes>
Windowed game play screen	-startwindowed

People
monster_human_grunt
monster_barney
monster_scientist
monster_generic
monster_gman

Monsters
monster_sentery
monster_headcrab
monster_alien_slave
monster_alien_grunt
monster_bullchicken
monster_zombie
monster_apache
monster_ichthyosaur
monster_bigmomma
monster_barnacle
monster_tentacle
monster_gargantuan
monster_nihilanth
monster_houndeye
monster_rat
monster_cockroach
xen_tree
xen_spore_small
xen_spore_medium
xen_spore_large

Corpses
monster_barney_dead
monster_scientist_dead
monster_hevsuit_dead

Key binding:
To activate codes easier, bind them to keys. For example, type /bind v "impulse 101" at the console window to bind the "HEV suit, weapons, and ammo " code to the "V" key.
Victor Chan.

Chat key bindings:
You can enter bind "p" "say Hello" or bind "p" "teamsay i need backup" and press [Enter] at the console window to bind those and other chat commands.
[EzB] Vash the Stampede.

Zoom on every weapon:
Get the Crossbow in single player mode and do a quick save with the weapon that you want to zoom in with. Change to the Crossbow and zoom in, then quick load and your other weapon will be zoomed in. You can now change weapons and they will all be zoomed in. To come out of zoom, change back to the Crossbow and press the second fire button until it zooms out again.
Ow and members of Clan [MaGinty] at Oscars Internet Cafe.

Hint: Completing We've Got Hostiles quickly:
As soon as you enter the "We've Got Hostiles" level, turn to your right and use the /noclip code to float through the glass window with the security guard being eaten by the zombie. When you are in there, press the switch that opens the Silo and the Silo door will open. Float back out of the room, disable the noclip code, then go through the Silo door to start the next level.
vavuip t, t olfseaw g, eie.

Hint: Defeating Gargantua:
It is possible to kill Gargantua when you meet him again in the parking lot. Immediately as you walk into the parking lot in the Incoming section of the game unload all your missile launcher ammunition, at least six grenades, and four Tau Cannon charged shotsm and how clip from a combat rifle to kill him.
Kris Colbert.

Hint: Advance to final Boss:
Enable the console window and go to the Hazard course. When you reach the bridge to get the hazard suit, jump of it into the sludge. You should be teleported to Nihilanth automatically.
Firehurtz.

Hint: HEV suit falls out:
Enable the /impulse 101 code while in mid-air and an error saying the hev suit has fallen out will appear.
Victor Chan.

Hint: Starting tips:
After the "accident", you will discover a scientist giving CPR to a security guard. Wait 15 to 20 seconds to see the outcome, which usually results in the security guard being revived. He is not useful at this time, but return to him after getting the crowbar. Kill him with the crowbar so he can not fire back to get his gun and ammunition.

Soon after this, you will ride an elevator upward. Have the gun ready. Shoot the monster attacking the security guard; a couple of shots should do it. This security guard can cover you until you reach the main entrance area.

One important tactic in the early game is to use your "allies" to your advantage. When you no longer require the services of a security guard, kill him and take his ammunition. A scientist is also useful in drawing enemy attack. Be careful not to harm an ally when another security guard is present, as he will attack you. Also be aware that monsters can sense your allies; and even if you crawl, monsters can hear your allies' walk.

The beginning of the game also has the following glitch. There is a scientist sitting in front of a damaged instrument panel, in the area of the first scientist who opened a door for you. This scientist is invincible. You can shoot or beat him with a crowbar, and all he will do is whine. This also saturates the area with a large amount of blood.
Kent Phillips.

Hint: Saving ammunition:
Do not waste precious pistol ammo on headcrabs. Use your crowbar, as it is more useful.
Ian.

Hint: Using the pistol:
Use the following trick to save ammo for all guns other than pistol. Most creatures or persons can be killed with five or less direct shots of the pistol.
billellen.

Crabs: 2 shots or 1 crowbar hit
Zombies: 4 shots
Electric Aliens: 3 shots
Trip Bomb: 1 shot
Machinegun on stand: 5 shots
Soldiers: 5 shots
Dogs: 3 shots
Spitters: 4 shots

Hint: Using guards:
If you have a guard, get him close enough and he will take care of almost anything for you. The only time you ever need to fire is if the creature is close to the guard.
billellen.

Hint: Rocket:
In the "Apprehension" level, you will reach a part where you go through two red doors reading "CAUTION" that lead into an area with a large sunken in area, two military officers, and a turret gun. Kill the two officers (you can use the turret gun if desired). Then, turn and face the direction opposite the wall with the door and the large window. Enable the "No Clipping" code and walk forward through the natural wall. You will see a large yellow shaft. When you get closer, you will see a huge rocket inside.
Calvin2367.

Hint: More powerful shotgun:
When using the shotgun, right click to shoot two shots at once. This kills everything twice as fast.
nookie162203.

Hint: Jump higher:
In multi-player on LAN games, create a game and choose a level with the Zapper in it. This is the gun that you hold the Right Mouse Button to charge and shoot. Aim it at the ground and you will jump high. Note: Be careful where you aim when you fall because you will lose health. This does not work in Story mode.
Boydanja.

Hint: Soft landings:
If you jump or fall from a high location, use the Tau Cannon Gun (gun hat fires orange bolts). When you fall, use secondary fire to hold it and release it just before you hit the ground. You will land without losing health. You can use this technique to get to high places by doing this from the ground.
newtontheemu.

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 /nocliping 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.
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: Grunt smell comment:
In the first level, enable the /impulse 101 code and go to either one of the two security officers (Barneys) guarding an area. Use the /impulse 76 code to spawn a Grunt near them. Do not spawn the Grunt in a wall or Barney or the game will end with an error message. Kill the Grunt quickly and leave it on the floor for a few seconds. Barney should say "Ew, what's that stench?" or something similar.
Jonathan Orengo.

Hint: Exploding scientists:
On the level where you are picking up your HEV suit before the accident, enable the /impulse 101 code and select the crowbar. Walk up to a scientist and wait for him to do a scripted event such as scratching his chin while looking at computer readings. Keep hitting him with the crowbar. When the scripted event ends, depending on how many times you have hit him, there will be an explosion of meaty chunks.
jhan.

Hint: Freeman's locker:
When you begin a game and get your suit, look at the lockers. One will be marked "Freeman" (your character's last name). Walk straight to it and you will see a photo of his little boy or girl.
mark.

Hint: Programmer reference:
Play the On A Rail level. In the dark place were you crawl through, look on the wall to see the word "Riller". Dave Riller is the name of someone in the starting credits.
kenthouse.

Hint: Barney gets cut in half:
When you enter the room where the lasers are shooting out the walls, run through. There should be a Barney (security officer) on the floor. Watch carefully and you can see the laser go across and literally cut him in half.
scott clary.

Hint: Spawn Barney in War with Nihilanth:
Normally when you want to spawn Barney at the Nihilanth episode, you will get an error message. To solve this problem, go to Lamba Core teleport to Xen. Enable the /noclip code/ After the scientist finishes his teleport to Xen, go through and dark. Then, type give monster_barney repeatedly until you arrive. You will go to a strange island and not have a Barney, but you must type it. After that, you can play and fight with Barney at the alien world. You also can do this at Nihilanth teleports. The v1.1.1.0 patch no longer allows this to happen.
Mohammad Arif.

Hint: See G-man and Gordon:
At the end of the game, after G-man asks you to choose between his employment or death, walk into the portal. As the credits start, enable the brightness 9999999999999 code. You will see G-man and Gordon standing next to each other. You can also enable the chase_active 1 code to get a better view. Note: This will also happen if you decline his offer. [Screenshot 1] [Screenshot 2]
Laytz94.

Glitch: Cheats on first level:
If the all weapons and ammo cheat code is used in the first level of the game, on the train, an error message stating that the hev suit fell out of level will appear. The game will automatically quit.
Patdelony.

Glitch: Changing voice:
There is a deep voiced scientist in level 1, in the room before the test chamber. When you ask him to go with you he will have a high pitched voice.
Patdelony.

Glitch: Dislocated body parts:
After the disaster, in anti-gore mode, choose any level and shoot down one of the men. He may not disappear. If he does not, keep hitting his bag with a crowbar (if visible). He should appear have all his body parts dislocated. Note: This sometimes works better if you creep up behind him with a crowbar or enable the /notarget code. To get in anti gore-mode, go to the options menu and use the password protected area on the visuals.
01lawreyanstis.

Glitch: Talk to dead man:
After the accident, when you go to the area where there is a scientist sitting on the floor and another is comforting him, enable the /impulse 101 code. When the man that is sitting down is talking, beat the standing man with your crowbar until he dies. When the old man is done talking, the dead man will talk to you.
Jeice728.

When you are done with the first part, after all of the destruction starts, you will be in a room where two scientists let you into the machine that you put the sample in. If they are dead, then this trick will work -- it is after the accident, and not before. Enable the /impulse 101 code and use the eye scanner that is lop sided, next to the door. Go through when it allows you to and you should see a scientist giving Barney CPR. Use any weapon, preferably the crowbar, and hit Barney. He will talk even though he is dead on the ground.
scott clary.

Kill A Barney or Scientist. If the body does not disappear, crouch next to it. Press [Use] and the Barney/Scientist should talk.
THE_AXE_WIELDING_POTATOE.

Glitch: Trapped scientist:
Just before the accident you will enter a room with two scientists. They will talk to each other. After they have finished and have opened the door, make one of the scientists stand on where the door should be. Once you go into the room, the door should shut behind you, with the scientist trapped in between it. Once you have put the rock into the laser, run into the room with the two scientists and hide out of sight from the laser. This should make the sequence to Zen not happen. When the next chapter starts, the scientist you trapped in the door should still be there.
Alex Feeney.

Glitch: Early dialogue:
When you first start the game, enable the /noclip code to jump out of the tram. Then, walk to the end of the pathway and jump down to the helicopter. Talk to the men in the cave to hear dialogue that should be from after the "accident" but are not.
Peter White.