While in game, pull and hold the Left Trigger. Note that these codes can only be used after they are unlocked.

Hold LT: and press A, RT, Y, RT, X, LB --> Bulletproof
While holding LT, press: X-B-A-LB-RT-Y --> Draw Enemy Health
Hold LB: and press A, B, A, LT, X, Y --> Infinite Assault Rifle Ammo
Hold LB: and press LT, Y, RT, B, LT, X --> Infinite Grenade Launcher Ammo
Hold LB: and press RT, B, X, LT, X, A --> Infinite Shotgun Ammo
Hold LB: and press B, Y, LT, RT, A, B --> Infinite SMG Ammo
in game, Hold LT then press Y + A + Y +X + LB + B --> One Shot Kill
While holding LT, press: LB-A-B-A-Y-RT --> Textureless Mode
Hold LB: and press Y, A, B, RT, Y, LT --> Wield Excalibur
Hold LB: and press A, RT, B, RT, LT, X --> Wield Soul Reaver