While your adrenaline is at 100 and starts to flash press the following buttons
Invisibility Power-Up: Right, Right, Left, Left Agility Power-Up: Down, Down, Up, Up Berserk Power-Up: Up, Up, Up, Up Regeneration Power-Up: Down, Down, Down, Down
Citadel
In order not to get hurt(from the fall or an enemy" on the citadel level "Capture the Flag" drop the teleporter device into the hole over the enemy flag and use the fight trigger to activate the camera look for anyone in there if there is no one drop in and even if there is, take a chance at least you know where they are.
Unlimited Tag Rifle
Glitch- In order to do this cheat you must aim the tag rifle at the sky hold in the R trigger holding in the R trigger (also reported as press X+B) cycle thru your weapons 2 making sure to land back on your tag rile then let go of the R trigger now you have unlimited ammo for it. If you shoot the shots left will go to 0 but you will still have unlimited ammo.
P.S if you change weapons after you did the cheat it will go away and you will have to do it over again.
Cursed Level secrets
1. When you are in the swamp near the skull that's on the base of the wall there is a lift taking you to the top of the level where you will find some wooden beams to walk across. There is a gap in the middle which you must jump and then continue along the wooden beam to what seems like a wall. Carry on and you will disappear through the wall where you will find some goodies(tip, This is a great place for camping when playing split screen with your mates, Just wait for them to come near and surprise them from nowhere).
2. There is a walkway with holes in the floor and two skulls either side at the top of the entrance to it.In the room before this with the two health pickups and the fallen down rocks you'll notice a section on the wall has a square outlined in it. This is a door in wich you'll find a Double Damage behind. take out your trusty assault rifle and shoot the block it lies behind.
