Half-Life

You must first enable the ''console'' (see elsewhere on the codes list), then in the game, open the console and type ''map x''. x represents the name of the level as listed below; for instance, type ''map c0a0'' for the first level.

A lot of the time you won't begin in the place you would if you accessed the map normally. You will sometimes need to use the No Clipping Mode to move out of the start positions.

Put Trip Mines onto a wall in form of a small staircase. You can actually jump on them and even use them to reach places you're not supposed to reach just yet or even places that aren't supposed to ever be reached like roofs that can be used as shortcuts.

First, enable the console. Then, type the proper code into it to get the desired effect.

Instead of ''C:SIERRAHalf-Lifehl.exe -console''

it's

''C:SIERRAHalf-Lifehl.exe -dev -console''

Otherwise the impulse cheats don't work.

In order to enable your console, (cheat box, basically) right click on the half life shortcut. Go down to properties. A box should open up with the properties. Go to the target tab. The line should look something like this: X:\Sierra\Half-Life\hl.exe . At the end of that put -console . Now it should look like X:\Sierra\Half-Life\hl.exe -console . Make sure that you are only using one space. Now, go back into Half Life. The main startup screen should have an extra selection that says console. Here you can enter cheats, see what's loading, and even kick people if you are on a server.

A technique used in a lot of Ego-Shooters is the Rocket-Jump where you point a Rocket Launcher at the ground and fire off a rocket while jumping to be able to jump way higher than usually. The downside is that you lose health by doing this and since a rocket in Half-Life takes away lots of health it wouldn't really be of good use.
Instead you can exploit another possibility in Half-Life: Using the secondary fire mode of the Gauss Cannon instead of the rocket launcher will also launch you high into the air but will not directly deal any damage (only eventual falling damage).

After activating the conlse, press tide (~) and enter the following.

Go to the start menu, then go to all programs, then go to accessesories, then click on command prompt. Select you Half-Life directory and type hl.exe -console then Half-Life should open. Start a new game then press the ` (tilde) key then type in these codes:

During the mission 'On A Rail' (the part of the game where you have to stop the rockets from firing and your in the sewers or something on a trolley). Turn on 'noclip' and float towards the top of the rocket. once you get to the top you can see a pic of a developer of the game. its his face tiled about 50 times on a square. there is a ladder at the top that brings you up another level with the same pic.

P.S - this Easter Egg is only reachable using 'noclip'. there is no other way to get up that high

You go to console and you have to type
X=any number,0-999
sv_gravity X
You should have only one space after gravity and before the number
It shoud look like this
sv_gravity 111