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