Quake II

Gold Cheat:
To get gold you must beat the game on hard. Winning gold will give you infinte ammo, all weapons and all the rest of the multiplayer codes you receive when you win silver and bronze.

Silver Cheat:
To enable Silver Cheat, finish the game in MEDIUM difficulty. This will open 2 more bars in multiplayer mode : Game Speed and Blast Force. Plus it will unlock the multiplayer cheats you get for winning bronze.

Bronze Cheats:
Beat the game on the easy difficulty. This will give you two options for multiplayer mode: Weapons Stay and One hit kill.

Kill Final Boss easily:
First when you enter the boss room strafe one step to the right so you see the tank commando and shoot him down with your rocket launcher when he's dead run forward to the flying enemy and run from right to left and shoot at him with your hyperblaster and when you dont have any more ammo take the minigun and do the same thing again. Then you shoot the other tank commander with your rocket launcher and when do the same thing to the flying enemy

Hidden multiplayer areas:
In the Hydophobia level, go into that hallway thats all red. Stop in the center and you'll notice a darkened area on the wall. Shoot it and it will reveal a BFG10K. There's another secret. In the pool of water by the super-shotgun, jump in and shoot the center of the wall by the shotgun to reveal a quad damage.

In Toxic Vats level,go into the narrow hallway with a ladder on each side. Take the ladder that brings you to the platform where you can get on the moving crane thingy. Take the hallway to the part where you're standing on the glass platform with the hyperblaster on it. look down through the glass and you'll be able to see a railgun submerged in a small section of the toxic waste. Jump in and swim down and get the railgun.

Invincibility:
Pause game and press L2, L2, R1, R2, R1, L2.

Infinite ammo:
Take the chaingun, which is weapon number 5 in the list, and then press the fire button. Keep holding it down, and then change your weapon to anything else. Now you should have unlimited ammo on your chaingun AND machine gun if you did it correctly. This may take a few tries.