Survive burning

After catching on fire, quickly press Start, then press Start again. You will be hurt, but still alive.

X-ray vision

The virus scanner may be used to look through the walls to find enemies.

Grenade launcher in level 1

Go out the window in the bar into the back alley. Look up to see two fire escapes. Climb onto the dumpster and get onto the fire escape opposite the bar first, then jump up to the pipes and go hand over hand to the other fire escape. Be careful, because two terrorists will run out to shoot half way across the pipe. After taking care of them, drop down onto the fire escape and open the box for the grenade launcher. This makes the grenade thrower in the subway section much easier to handle.

Getting through the subway

Go to the opposite end of the subway after it explodes. Use the flashlight on the left of the tracks to find the C-4. Get the C-4, then go to the right hand side. Look up to see the upper level. Press Triangle to climb onto the red crate. Press Triangle to keep climbing up through the debris until the top is reached. This is the only way to exit the lower level.

Museum gates

Find the card keys to get through the gates in the museum. Check all the guards and people that are killed; they usually carry card keys. For the gate in the Rocket Room, shoot the control panel on the third level that keeps sparking while your character is standing on the elevator to reach to that level. The man with the card key is up there.

Defeating Rhoemer

The only way to defeat Rhoemer (the final boss) is with Gas grenades, which can be found in the upper right room of the last level. -From: exocet78.com

Note: This code also gives enemies infinite armor. So the only way to kill an enemy or to be killed is by a shot in the head or an explosion.