Enter the cheats under gamepla - Half-Life
Feb 25th 2005, ID#5891
Enter the cheats under gameplay by pressing ¬ß or |. Then you should get a screen coming down, if not, try reinnstall Half-Life.
God: This cheat makes you invincible.
Notarget: Your ennmies can't see you
Impulse 101: Ammo, weapons and armor.
You don't have to enter the cheats everytime you need ammo or other things, you just press the up button (not w but the other)