Half-Life 2 Cheats

Spawn medpak
Press [Up], [Up], [Down], [Down], [Left], [Right], [Left], [Right], [B], [A] during game play to spawn a medpak that will restore 25 points of health.

Restores ammo for current weapon
Press [Y], [B], [A], [X], [White], [Y], [X], [A], [B], [White] during game play.

Unlocks all chapters
Press [Left], [Left], [Left], [Left], [Black], [Right], [Right], [Right], [Right], [White] during game play.

Follow Freeman: Item room
You will hear the metal device where you get two people to follow you. After it is done, you will see a room to go through. You can find items there, but be careful; sometimes you may die. Save the game before entering it.

Getting past turrets and other dangerous enemies
When you need to run a long way in front of you and you have some objects with you (for example, a non-explosive barrel), if you have the gravity gun, pick it up. Use it as cover and run (while facing the enemy) to the other side. Then if possible, shoot the barrel at the enemy. Note: Make sure there are no more that one enemy while doing this. Also make sure that the object is indestructible, and most importantly, look at the enemy and see if you can kill him or it with one shot.