Complete the following achievements to unlock Xbox Live Gamerscore points. 

Achievement                            How to unlock 
---------------------------------------------------------------------
...And Justice For All (50 points) - Verify all high value targets
Armaggedon It (20 points) - Destroy 20 buildings
Balls to the Wall (20 points) - Beat the Winching Challenge three times
Be Quick or Be Dead (10 points) - Snipe 50 enemy vehicle drivers
Billion Dollar Babies (25 points) - Earn $1 billion
Damage, Inc. (50 points) - Use 20 airstrikes in co-op
Digital Man (20 points) - Unlock all shop items
Eat the Heat (10 points) - Try accelerating and braking at the same time
Everybody Wants Some!! (50 points) - Play with a Mercenaries 2 developer 
Gone Shootin' (20 points) - Complete one of Fiona's challenges
Hail and Kill (20 points) - Destroy 50 objects using melee
Heavy Metal Thunder (10 points) - Successfully complete 10 action hijacks
Highway to Hell (10 points) - Complete three different races
Holy Smoke (20 points) - Destroy 50 objects with a grenade
Little Savage (20 points) - Destroy 50 objects with an RPG launcher
No More Mr. Nice Guy (10 points) - Make all factions hostile
Nothin' But a Good Time (50 points) - Destroy 200 objects from the gunner seat
Partners in Crime (50 points) - Play co-op with a friend
Pipeline (20 points) - Capture all outposts for a single faction
Shoot to Thrill (20 points) - Get 25 headshots
Tattooed Millionaire (25 points) - Earn $1 million
We'll Burn the Sky (50 points) - Unlock all landing zones
Wheels of Steel (50 points) - Come in first during a co-op race