At the 'Customize Officer' screen highlight the $1 Avatar and press R to spin him. When he has completed two full rotations stop the spin so that he is facing away from you and then press Triangle, X, Triangle, X, Triangle, Circle. If you have entered the code correctly a confirmation message will appear on screen and return you to the 'Main' menu where you will be able to customize and buy the avatar.

Unlocking Slipknot and Chimaira:

Slipknot 0 - Mission 5:
Kill one Zombie by the Slipknot sign

Slipknot 1 - Mission 7:
Kill one Zombie by the Slipknot sign

Slipknot 2 - Mission 10:
Kill one zombie by the Slipknot sign

Slipknot 3 - Mission 13:
Kill one Zombie by the Slipknot sign

Slipknot 4 - Mission 16:
Kill one Zombie by the Slipknot sign

Slipknot 5 - Mission 20:
Kill one Zombie by the Slipknot sign

Slipknot 6 - Mission 23:
Kill one Zombie by the Slipknot sign

Slipknot 7 - Mission 26:
Kill one Zombie by the Slipknot sign

Chimaira Mission 29:
Kill one Zombie by the Chimaira sign

Slipknot 8 - Mission 31:
Kill one Zombie by the Slipknot sign


Unlock Bloodrayne:
Complete ALL missions

Unlock Santa Claus:
Complete ALL missions

Unlock Bloodrayne - Alternate method:
Get a Gold Medal on mission 33