These are the new achievements added via Live, they are all multiplayer. Worth 75 gamer points total.
Achievement
How to unlock
Assassin (Multiplayer)
Find and kill an opponent who has the Assassin Achievement.
Crack Shot (Multiplayer)
Kill 10 players with gunshots and at least 5 gamertags in the room without reloading or dying.
Explorer (Multiplayer)
Win 5 Team or Solo matches on each original MP map with at least 5 different gamertags in the room.
Team Player (Multiplayer)
Win 30 co-op matches with at least 6 gamertags in the room.
Victor (Multiplayer)
Win a public player match in all original game types with at least 5 different gamertags in the room.
Assault On Norad: Invisible rocket launcher
After killing Carlos Ontiveros, run towards where his body fell off the roof. Pick up his rocket launcher. You will not be able to see it, but still see your character holding it. The rocket launcher will still fire rockets.
Bulldog: Ghost rocket launcher
On the "Bulldog" level, after you complete the first part and are able to select your group, choose the antitank gunner. When you get the chance, kill him. Do not try to revive him and wait for him to die completely. Once he dies, his rocket launcher will disappear but you can still pick it up. You will not see anything in your hands and you can still fire the weapon. The rockets will come from wherever you killed the antitank gunner.
Falcon weapon
Destroy 100 helicopters in Multiplayer mode to unlock the Falcon weapon.
Gamerscore points
Accomplish the indicated task to get the corresponding number of Gamerscore points:
Complete the training mission (25 points): Successfully complete the training mission.
Heavyweight in multiplayer (20 points): Get a total of 10,000 kills in multiplayer.
Deadly in multiplayer (20 points): Get 4 kills in 4 seconds or less in multiplayer.
Unyielding in multiplayer (32 points): Get 30 kills before being killed in multiplayer.
Falcon in multiplayer (16 points): Shoot down 100 helicopters in multiplayer.
Sniper in multiplayer (36 points): Get a career total of 500 head shots in multiplayer.
Committed in multiplayer (28 points): Play for 8 hours straight in multiplayer.
Master of Ceremonies (24 points): Host at least 1000 matches.
Coop 1-1 (8 points): Win missions in the cooperative campaign.
Coop 1-2: Win missions in the cooperative campaign.
Coop 1-3 (8 points): Win missions in the cooperative campaign.
Coop 1-4 (8 points): Win missions in the cooperative campaign.
World Champion in multiplayer (40 points): Climb to the top of the universal leaderboard.
Solo champion in multiplayer (32 points): Climb to the top of the solo leaderboard.
Team champion in multiplayer (32 points): Climb to the top of the team leaderboard.
Reach Ramirez under normal (25 points): Reach Captain Ramirez's position.
Secure Ballantine under normal (25 points): Secure the U.S. President.
Escort Ruiz-Pena under normal (25 points): Escort the Mexican President to U.S. Embassy.
Neutralize rebel outpost (norm.) (25 points): Neutralize a rebel outpost blocking the highway.
Eliminate defenses under normal (25 points): Eliminate Chapultepek castle defenses.
Secure U.S. tanks under normal (25 points): Take control of 50 U.S. tanks stolen by rebels.
Protect U.S. President under normal (25 points): Locate and protect U.S. President.
Reach the Football under normal (25 points): Reach the Football's location.
Clear the way under normal (25 points): Clear access to rebel HQ.
Capture Ontiveros under normal (25 points): Capture General Ontiveros alive.
Locate the Football under normal (25 points): Take the Football back from Carlos Ontiveros.
Reach Ramirez under hard (25 points): Reach Captain Ramirez's position.
Secure Ballantine under hard (25 points): Secure the U.S. President.
Escort Ruiz-Pena under hard (25 points): Escort the Mexican President to U.S. Embassy.
Neutralize rebel outpost under hard (25 points): Neutralize a rebel outpost blocking the highway.
Eliminate defenses under hard (25 points): Eliminate Chapultepek castle defenses.
Secure U.S. tanks under hard (25 points): Take control of 50 U.S. tanks stolen by rebels.
Protect U.S. President under hard (25 points): Locate and protect the U.S. President.
Reach the Football under hard (25 points): Reach the Football's location.
Clear the way under hard (25 points): Clear access to rebel HQ.
Capture Ontiveros under hard (25 points): Capture General Ontiveros alive.
Locate the Football under hard (25 points): Take the Football back from Carlos Ontiveros.
Perfect Chapter 1 in multiplayer (40 points): Successfully complete all primary and secondary objectives in Chapter 1.
Get on roof in Treasury level
In the Treasury level, it is possible to get up on the roof of the treasury. Have your pistol or grenade equipped in order to run faster. Run directly at the back door and dive into it; do this by running and quickly clicking the Right Analog-stick. Make sure your head hits the door and you should teleport to the roof. This also works on the level with the wall. You can teleport up into the rooms on the ends of the wall. Note: This may require some practice and should work with any building with an overhanging ledge that you can dive under.
GRAW: Fly
Go by the last seen spot of the V.I.P. Dive out in front of the car and switch to assault. Call the team to regroup and go forward while lying down. You will fly a few inches above the ground.
Infinite ammunition
Pause the game, then hold LT + RT + Back and slowly press RB(2), LB, X, LB, Y. If you entered the code correctly, you will hear a sound.
Invincibility
During gameplay press start to pause the game then while holding down the back button and the left and right triggers press Y,Y,X,RB,X,LB. You'll hear a chime to confirm that the code was accepted.
Invincible team
While playing a game press Start to pause the game and hold LT + RT + Back while pressing X, X, Y, RB, Y, LB. If you did this correctly you will hear a sound.
Lase the power generator
During the mission you will be given an objective to lase the power generator. To do this, you must press Up on the d-pad until you see the Apache helicopter appear in NORCAM on the top left of the screen, target the power generator with your gun until it lights up in yellow, and press Up on the d-pad again to have the Apache blow up the generator.
Regain 100% health
While playing a game press Start to pause the game and hold LT + RT + Back while pressing LB, LB, RB, X, RB, Y. If you did this correctly you will hear a sound.
Scott Mitchell invincibility
While playing a game press Start to pause the game and hold LT + RT + Back while pressing Y, Y, X, RB, X, LB. If you did this correctly you will hear a sound.
Scott Mitchell invincible
While holding the "back" button, LT, and RT, press Y, Y, X, RB, X, LB.
The green helth indicator will stay green throughout the mission
The code must be re-entered after each mission or after the game has been stopped and resumed.
Slip and slide
While running, quickly click the Left Analog-stick to slide along the ground or click and hold the Left Analog-stick to do a sort of belly flop and slide on your stomach.
Sniper Rifle
Get over 500 total head shots in Multiplayer mode to unlock the Sniper Rifle.
To get a lot of kills to Co-op Terroitorys on Xbox Live
When on Old Town map on Co-op Terroitory, to the right stair go down close to the middle stair and lie down. The cpu will go pass you and always turn to the left stair. Start shooting at them. Sometimes they will find you and shoot you. It took 10 minute to kill me on a 15 minute match and I had 450 kill by the end of the match. Trust me this cheat always works.
Unlimited ammo
While playing a game press Start to pause the game and hold LT + RT + Back while pressing RB, RB, LB, X, LB, Y. If you did this correctly you will hear a sound.
Various Codes
For the level code, enter the sequence at the mission select screen. For the other codes, you'll need to pause the game, and while at the pause menu hold down the Back button, Left Trigger, and Right Trigger before entering the password string.......
Cheat Effect
Y, RB, Y, RB, X - ALL LEVELS
LB(x2), RB, X, RB, Y - FULL LIFE
Y(x2), X, RB, X, LB - SCOTT MITCHELL INVINCIBLE
X(x2), Y, RB, Y, LB - TEAM INVINCIBLE
RB(x2), LB, X, LB, Y - UNLIMITED AMMO
Warfighter mode
Successfully complete the game on any difficulty setting to unlock the Warfighter difficulty setting.