Killzone: Liberation (PSP)

Cobar
Beat Hard mode.

Commando
Beat the game in 2-player co-op on any difficulty.

Metrac
Beat Easy, Normal, and Hard modes.

Stratson
Win 100 times in MP(ad-hoc or infrastructure).

Specialist
Win 10 games in Ad-Hoc or Infrastructure Multiplayer.

Unlock Concept art pack #1
Finish Single Player Campaign 3-4 on Normal.

Unlock Indepth character profiles #1
Finish Single Player Campaign 1-1 on Easy.

Unlock Indepth character profiles #4
Finish Single Player Campaign 4-4 on Easy.

Unlock Jukebox
Finish Single Player Campaign 2-4 on Normal.

Unlock Multiplayer Character: Cobar
Finish Single Player Campaign 4-4 on Hard.

Unlock Multiplayer Character: Evelyn
Finish Single Player Campaign 4-4 on Normal.

Unlock Wallpaper pack #1
Finish Single Player Campaign 1-4 on Easy.

Unlockable abilities
You can access the ability selection screen by pressing square on the weapon selection screen. Abilities are unlockable bonuses that let you do certain things, like carrying 3 grenades or having 50% more health. You can unlock these abilities by aquiring a certain amount of points. Points can be collected by completing challenges.

Effect - Code

Unlock 50% More health - 300 Points
Unlock C4 Placement twice as fast - 100 Points
Unlock Carry 3 Grenades - 020 Points
Unlock Carry 3 Smoke grenades - 140 Points
Unlock Carry 3 Syringes - 060 Points
Unlock Carry 4 Pressure Mines - 220 Points
Unlock Carry Unlimited ammunition - 480 Points
Unlock Close Combat damage doubled - 260 Points
Unlock Trip Mines disarmed twice as fast - 180 Points
Unlock Your Buddy has 50% more health - 340 Points