These are copied directly from my Official Guide, which i bought at CC today.
SPARTAN
EVA-
Body: Complete Tsavo Highway on Normal, Heroic, or Legendary
Shoulders: Complete The Ark on Normal, Heroic, or Legendary
Head: Complete Campaign on Normal
EOD-
Body: Complete Tsavo Highway on Legendary
Shoulders: Complete The Ark on Legendary
Head: Complete Campaign mode on Legendary
Security-
Shoulders: Earn 750 Gamerscore points
Head: Earn 1000 Gamerscore points
Scout-
Body: Unlock "Too Close to the Sun" Achievement
Shoulders: Unlock "We're in for some Chop" Achievement
Head: Unlock "Used Car Salesman" Achievement
Mark V-
Head: Unlock "UNSC Spartan" Achievement
ODST-
Head: Unlock "Spartan Graduate" Achievement
Rogue-
Head: Unlock "Spartan Officier" Achievement
Achievements needed to unlock:
Too Close to the Sun-Destroy an enemy Banshee with the Spartan Laser or Missile Pod in a ranked Playlist or in Campaign.
We're in for some Chop-Destroy an enemy vehiclewith equiptment in a ranked playlist or in Campaign.
Used Car Salesman-Destroy a vehicle that has three enimies in it in a ranked playlist or in Campaign.
UNSC Spartan-earn your Sergeant rating to be recognized as a true Spartan (Online).
Spartan Graduate-Earn 5 EXP or finish 10 games to complete the requirement for basic training (Online).
Spartan Officier-Advanced to the Spartan Officer ranks (Online).
ELITE
Flight-
Body: Complete Tsavo Highway on Heroic or Legendary
Shoulders: Complete The Ark on Heroic or Legendary
Head: Complete Campaign mode on Heroic
Ascetic-
Body: Unlock "Up Close and Personal" Achievement
Shoulders: Unlock "Overkill" Achievement
Head: Unlock "Steppin' Razor" Achievement
Commando-
Body: Unlock "Triple Kill" Achievement
Shoulders: Unlock "Killing Frenzy" Achievement
Head: Complete "Overkill" Achievement
Achievements needed to unlock:
Up Close and Personal-Kill 5 enemies via melee or assasination in a ranked free for all playlist (online).
Overkill-Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (online).
Steppin' Razor-Score a triple kill with an Energy Sword in a ranked free for all playlist (online).
Triple Kill-Kill 3 enimies within 4 seconds of one another in a ranked free for all playlist (online).
Killing Frenzy-Kill 10 enemies without dying in any ranked free for all playlist (online).
THE FLOOD
Infection Form
Carrier Form
Combat Form
Pure Form-
Stalker-Melee's you.
Ranged-Shoots you with spikes that grow from its skin.
Tank-Spits infectous forms while it tries to steam roll you.
NEW VEHICLES
Anti Aircraft Wraith- Dual supercharged Fuel Rods guns replace the plasma morter.
MULTIPLAYER MAPS
Construct
Epitaph
Guardian
High Ground
Isolation
Last Resort
Narrows
Sandtrap
SnowBound
The Pit
Valhalla
-X
SPARTAN
EVA-
Body: Complete Tsavo Highway on Normal, Heroic, or Legendary
Shoulders: Complete The Ark on Normal, Heroic, or Legendary
Head: Complete Campaign on Normal
EOD-
Body: Complete Tsavo Highway on Legendary
Shoulders: Complete The Ark on Legendary
Head: Complete Campaign mode on Legendary
Security-
Shoulders: Earn 750 Gamerscore points
Head: Earn 1000 Gamerscore points
Scout-
Body: Unlock "Too Close to the Sun" Achievement
Shoulders: Unlock "We're in for some Chop" Achievement
Head: Unlock "Used Car Salesman" Achievement
Mark V-
Head: Unlock "UNSC Spartan" Achievement
ODST-
Head: Unlock "Spartan Graduate" Achievement
Rogue-
Head: Unlock "Spartan Officier" Achievement
Achievements needed to unlock:
Too Close to the Sun-Destroy an enemy Banshee with the Spartan Laser or Missile Pod in a ranked Playlist or in Campaign.
We're in for some Chop-Destroy an enemy vehiclewith equiptment in a ranked playlist or in Campaign.
Used Car Salesman-Destroy a vehicle that has three enimies in it in a ranked playlist or in Campaign.
UNSC Spartan-earn your Sergeant rating to be recognized as a true Spartan (Online).
Spartan Graduate-Earn 5 EXP or finish 10 games to complete the requirement for basic training (Online).
Spartan Officier-Advanced to the Spartan Officer ranks (Online).
ELITE
Flight-
Body: Complete Tsavo Highway on Heroic or Legendary
Shoulders: Complete The Ark on Heroic or Legendary
Head: Complete Campaign mode on Heroic
Ascetic-
Body: Unlock "Up Close and Personal" Achievement
Shoulders: Unlock "Overkill" Achievement
Head: Unlock "Steppin' Razor" Achievement
Commando-
Body: Unlock "Triple Kill" Achievement
Shoulders: Unlock "Killing Frenzy" Achievement
Head: Complete "Overkill" Achievement
Achievements needed to unlock:
Up Close and Personal-Kill 5 enemies via melee or assasination in a ranked free for all playlist (online).
Overkill-Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (online).
Steppin' Razor-Score a triple kill with an Energy Sword in a ranked free for all playlist (online).
Triple Kill-Kill 3 enimies within 4 seconds of one another in a ranked free for all playlist (online).
Killing Frenzy-Kill 10 enemies without dying in any ranked free for all playlist (online).
THE FLOOD
Infection Form
Carrier Form
Combat Form
Pure Form-
Stalker-Melee's you.
Ranged-Shoots you with spikes that grow from its skin.
Tank-Spits infectous forms while it tries to steam roll you.
NEW VEHICLES
Anti Aircraft Wraith- Dual supercharged Fuel Rods guns replace the plasma morter.
MULTIPLAYER MAPS
Construct
Epitaph
Guardian
High Ground
Isolation
Last Resort
Narrows
Sandtrap
SnowBound
The Pit
Valhalla
-X
