Black Ops Skull Head costume:
To unlock the Black Ops Skull Head costume, beat the game and get all skillpoints on Superhuman difficulty.

Superhuman difficulty:
To unlock Superhuman difficulty, beat the game on Hard difficulty.

Cloven uniforms:
In online multiplayer mode go to "Soldier Loadout", press start, then enter the corresponding password to unlock the following items:

Cloven Bandana - 8cba 3462 6595 14d4
Cloven Helmet - f6e0 fa3e f1f4 61e1
Cloven Helmet w/ Bandana - a7f6 6e7c 05ec 1728
Cloven Bearded Head - d708 6b08 0f1c b5f6
Cloven Skin - a8f4 d189 68f8 559e

Hybrid skin cooling apparatus:
When in the Hybrid skin you can turn off your cooling apparatus by pressing L2. This allows you to sprint and see through walls.

Human skin sprint:
While running in the Human skin you can sprint faster by tapping L2.

Multiplayer medals:
Unlock the following medals by performing the corresponding tasks in online multiplayer mode:

Assassin - Kill 20 enemies in a row without dying.
Auger Marksman - Kill 100 enemies with the auger.
Base Defender - Get 2000 defensive kills across all game modes.
BBQ Chef - Kill 100 enemies with the L11-2 dragon.
Elite Soldier - Kill 10 enemies in a row without dying.
Fanatic - Compete in 1000 online matches.
Fry Cook - Kill 100 enemies with the arc charger.
Ghost - Get 100 stealth kills.
Going Commando - Get 100 node or flag captures.
Grenadier - Kill 100 enemies with grenades.
Heavy Weapons Expert - Kill 100 enemies with rockets.
Helping Hand - Get 100 assist kills.
Hero - Play 200 ranked matches and place first at least 60 times.
Legend - Play 300 ranked matches and place first at least 100 times.
Marksman - Kill 100 enemies with the M5A2 carbine.
Martial Artist - Get 30 melee kills.
Nathan Hale - Complete a single player game.
Ninja - Get at least 60 melee kills.
Precise Shot - Finish 10 matches with an accuracy of least 85%.
Professional - Get 100 headshots.
Reclaimer - Get 200 node or flag recaptures.
Savant - Play 100 ranked matches and place 1st 30 times.
Sharpshooter - Kill 100 enemies with the L23 fareye.
Shotgunner - Kill 100 enemies with the rossmore 236.
Tagger - Kills 100 enemies with the bullseye.
Unerring Aim - Finish 20 matches with an accuracy of least 85%.
Unknown - Compete in 5000 online matches.
Up Your Arsenal - Get 100 kills with every weapon.

Skill points:
Earn skill points by completing the corresponding tasks:

Acupuncture Is Cheaper - Kill 3 enemies at once with the hedgehog.
Reading Is Fun! - 10 intelligence reports.
Chicks Dig Eyestrain - 20 intelligence reports.
Chimera Pate - Run over 10 enemies with the tank in york.
Gasping for Air - Kill 2 hybrids in a level only after severing all of their hoses.
In For a Penny - Kill 3 hybrids with a single grenade.
Homing Beacons - Tag 4 hybrids with the bull’s-eye.
Tag, You're It! - Kill 5 enemies with the bull’s-eye in 30 seconds.
Turrets - Use the chimeran sentry gun to kill 6 enemies.
Lightfoot - Take no damage from the mines in manchester.
Nowhere to Hide - Kill 5 enemies in a level by shooting them through a wall with the auger.
This is My Rifle, This is My Gun - Kill the stalker in manchester traffic circle using only the M5A2.
Supersonic Meat Cubes - Kill 3 leapers with a frag grenade.
Too Many Secrets - Collect all intelligence reports.

Multiplayer skins/items:
Reach the following levels to unlock the corresponding items:

Level 01: Private Status - US Solider Body, Head 1 and 2, Small Helmet, American Standard and Dirty Uniforms.
Level 04: Private First Class Status - UK Solider Body, British Green Uniform, Canteen 2.
Level 07: Corporal Status - British Brick Uniform, Grenade Pouch, Leather Packs.
Level 10: Sergeant Status - Pouches, Medic Helmet 2, Head 3.
Level 13: Gunnery Sergeant status - Beret, American Camouflage Uniform.
Level 16: Staff Sergeant Status: British Goggles, Radio, Binoculars.
Level 19: 1st Class Sergeant Status - Commando Body, Commando Standard Uniform, Head 4.
Level 22: Sergeant Major Status - Commando Camoflauge Uniform, Belt knife, Backpack.
Level 25: Sergeant Major Status - Chest Pouches, Head Pouches, Head 5.
Level 28: Sergeant Major of the Army Status - Medic Helmet, Bedroll 1, Chute Pack.
Level 31: Lieutenant Status - Head 6, British Desert Uniform, VTOL Pilot skin.
Level 34: Captain status - Bedroll 2, Pouches, Pouch (Fanny Pack).
Level 37: Major Status - Head 7, British Helmet, Backpack.
Level 40: Lieutenant Colonel Status - Commando Leather Uniform, Chest Radio, Shirtless skin:
Level 43: Colonel Status - Camouflage Helmet, Leather Backpack, Back Holster.
Level 46: Brigadier General Status - Head 8, Canteen 1, Radio.
Level 49: Major General Status - Winters skin, American Advanced Uniform, Hip Bag.
Level 52: Lieutenant General Status - Head 9, American Helmet, American Arctic Uniform, Canteen.
Level 55: General Status- Cartwright skin, Leather Pouch, Canteen.
Level 58: Supreme Commander Status - British Camouflage Uniform, Knife, Head 10.
Level 60: Supreme Commander (3 PIPS) Status - Nathan Hale Skin, Belt Packs, Shovel, Backpack.

More skins:
Unlock the following skins by performing the corresponding tasks:

Mechanic Skin - All skill points in campaign mode -
Cloven Skin - Register at http://myresistance.net and go to your profile for a unique online code
Black Ops skin - Complete Campaign Mode on Superhuman
Black Ops skin with skull head - Complete Campaign Mode on Superhuman with all skill points

Unlockable rewards:
Unlock the following rewards by performing the corresponding tasks:

Concept Art Pack 1 - Earn 10 skill points.
Concept Art Pack 2 - Earn 20 skill points.
The Mighty Wrench - Earn 40 skill points.
Flip Levels - Earn 70 skill points.
Clank Backpacks - Earn 100 skill points.
MP Mechanic Skin - Earn 126 skill points.
MP Soldier Skin - Beat the game on superhuman mode.
Movie Player - Beat the game.

Unlockable weapons:
Complete the game on Campaign mode to unlock the following weapons:

-Arc Charger
-Backlash Grenade
-L11-2 Dragon
-Reaper
-Splitter

Cinematic:
To unlock the Cinematic entitled "Stranger Than Fission", beat the game. To view it, go to "Main Menu" > "Options" > "Cinematics".