Full list of all 47 Halo 3: ODST achievements worth 1,000 gamerscore. It takes around 25-30 hours to unlock all of the achievements on Xbox 360.
Scored over 200,000 points in Firefight on Crater.
Scored over 200,000 points in Firefight on Lost Platoon.
Scored over 200,000 points in Firefight on Last Exit.
Scored over 200,000 points in Firefight on Security Zone.
Scored over 200,000 points in Firefight on Rally Point.
Scored over 200,000 points in Firefight on Windward.
Scored over 200,000 points in Firefight on Chasm Ten.
In Firefight, on any mission, passed the 4th Set on 4-player Heroic LIVE co-op.
Scored over 200,000 points in Firefight on Alpha Site.
Completed Highway on 4-player Legendary LIVE co-op, with Iron, and no 'Hog or Scorpion.
Killed no Engineers in the city at night during entire campaign, alone or with another ODST.
Plasma Pistol Overcharged and quickly killed 10 Brutes.
Finished any level solo on Legendary, on LIVE, with no shots fired or grenades thrown.
Found all Audio Logs, alone or with another ODST.
Killed 10 enemies with the Flamethrower on Data Hive.
Got 10 Spartan Laser kills on ONI Alpha Site.
Got 10 Rocket kills on Kizingo Boulevard.
Killed 10 Engineers in the city at night, alone or with another ODST.
Found 15 Audio Logs, alone or with another ODST.
Killed all Wraiths in Uplift Reserve.
Stunned a vehicle with an overcharged plasma pistol and quickly killed the driver.
Completed Tayari Plaza and unlocked the Buck character in Firefight.
Completed Kizingo Blvd. and unlocked the Mickey character in Firefight.
Got 5 sticky grenade kills in any level.
In Firefight, finished a full round without killing a single enemy.
Got 10 Needler supercombine kills on any covenant.
Completed Legendary and unlocked the Dare character in Firefight.
Completed the Campaign on Heroic difficulty.
Completed the Campaign on Normal difficulty.
Completed Coastal Highway and unlocked the Last Exit Firefight mission.
Completed Data Hive and unlocked the Chasm Ten Firefight mission.
Completed Kikowani Station on Normal, Heroic, or Legendary.
Found the final clue unraveling the mystery, alone or with another ODST.
Completed NMPD HQ and unlocked the Romeo character in Firefight.
Got 15 headshot kills on NMPD HQ.
Completed ONI Alpha Site and unlocked the Alpha Site Firefight mission.
Finished any level with at least one Skull activated.
Traded weapons with a fellow character.
Found the 3rd clue unraveling the mystery, alone or with another ODST.
Completed Uplift Reserve and unlocked the Dutch character in Firefight.
Found 3 Audio Logs, alone or with another ODST.
Found the first Audio Log.
Got 10 automag headshot kills in any level.
Found the first clue unraveling the mystery.
Accessed and downloaded the city map to your VISR.
Killed 5 enemies while using VISR mode.
Found the first Medical Kiosk and healed yourself.