Put in the code MARTIAL

Successfully complete The Exchange level to unlock the Zoe Nightshade card, Oddjob and
Baron Samedi in multi-player mode, and Pistol upgrade.

Put in the code ASSASSIN

Enter "BLIMP" as a code at the "Secret Unlocks" screen.

Put in the code JANUS

Enter "ASSASSIN" as a code at the "Secret Unlocks" screen.

Put in the code BLIMP

Successfully complete the Countdown level to unlock the Drake card and Explosive Scenery
in multi-player mode.

Put in the code PARADISE
  
Get Nightshift Level
  
Put in the code HIGHRISE

Enter "PASSPORT" as a code at the "Secret Unlocks" screen.

Put in the code BONSAI

Enter "NUMBER 1" as a code at the "Secret Unlocks" screen. Note: There is a
space in the code.

Put in the code BITESIZE

An easy way to kill the guards that are on the snowmobiles, is to shoot them off, so that
the snowmobile is all that remains.

Enter "POWDER" as a code at the "Secret Unlocks" screen.

Put in the code NUCLEAR

Successfully complete the Double Cross level to unlock the Mayhew card, Uplink
multi-player mode, Sniper Rifle upgrade, and Xenia Onatopp in multi-player mode.

On the Enemies Vanquished level during racing
  pause the game and HOLD L and press B, B, X, X, Y

Enter "BOOM" as a code at the "Secret Unlocks" screen.

Put in the code HEADCASE