The following is a complete list of ALL the unlockables in the game and the required task to unlock them.

25 To Life Decal Level 1:
Take Two Human Shields

Freeze's Starting Outfit Level 1:
Get to your car

Flaming Beanie Level 1:
Defeat 20 enemies

Barbed Wire Hat Level 2:
Defeat 25 enemies

Black Bandanna Level 2:
Cover up 4 tags

Rick Ta Life outfit Level 2:
Return to your car

Bank Robbing Outfit Level 3:
Escape to your Getaway car

Westside Knife Tat Level 3:
Defeat 25 enemies

Gold Earrings Level 3:
Shoot ALL ATMs

Holster Level 4:
Achieve 20 percent accuracy

Kneepads Level 4:
Arrest 5 felon criminals

Tactical Vest Level 4:
Keep partner alive

ATF Decals Level 5:
Arrest 4 dealers

Officers Williams Level 4:
Take the evidence to Mendoza's car

DJ Envy Outfit Level 5:
Get to the subway

Riot Helmet Level 5:
Get 8 head shots

Big Mustache Level 5:
Get 25% accuracy

Big 'Dawg' Tattoo Level 6:
Get 30% accuracy

Full Tactical Harness Level 6:
Free a police officer

Sideburns Level 6:
Defeat 24 enemies

Shaun's Getaway Outfit Level 6:
Trap Shaun in a subway traincar.

Shaun's TJ outfit Level 7:
Find Riggs at the club

Mexican Flag Bandanna Level 7:
Paint over 4 Gang tags

Clock Cap Decal Level 7:
Defeat 60 enemies

Chest Tattoo Level 8:
Defeat 45 enemies

Scorpion Black Tattoo Level 8:
Get 12 headshots

Federates Outfit Level 8:
Escape with loot

Triple Bracelets Level 8:
Rob 5 cash carts

Camo Pants Level 9:
Defeat 32 enemies

Chest Flame Tattoo Level 9:
Get 16 headshots

Freeze's Prison Outfit Level 10:
Complete level

Chinese Pain Tattoo Level 10:
Protect Lazarus

No Parole Decal Level 10:
Defeat 30 enemies

Freeze's Mall Outfit Level 11:
Complete level

Red Hightops Level 11:
Complete level without dying

Black Gloves Level 11:
Get into 5 ATM's

Bulldog Chain Level 12:
Find ALL 5 secret stashes

Daz and Tech Tattoo Level 12:
Kill Shaun

G Cap Decal Level 12:
Defeat 30 enemies

Unlock Dazz:
Serve Shaun some justice.

Unlock Tech H9ne:
Serve Shaun some justice.

Unlock Freeze's Starting Outfit:
Get to your car.

Unlock 'Rick Ta Life':
Get to your car.

Unlock DJ Envy:
Get to the subway.

Unlock Shaun's Getaway Digs:
Trap Shaun in subway train.

Unlock Officer Williams:
Get the evidence to Mendoza's car.

Unlock Kurupt:
Find Saragosa and kill him.

Unlock Bank Robbing Outfit:
Escape to your getaway car.

Unlock Bonus Level 'Beatdown':
Complete ALL 12 missions and mission objectives.