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.
Completed Legendary and unlocked the Dare character in Firefight.
Completed the Campaign on Normal difficulty.
Completed the Campaign on Heroic 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.
Completed NMPD HQ and unlocked the Romeo character in Firefight.
Completed ONI Alpha Site and unlocked the Alpha Site Firefight mission.
Finished any level solo on Legendary, on LIVE, with no shots fired or grenades thrown.
Finished any level with at least one Skull activated.
Killed 10 enemies with the Flamethrower on Data Hive.
Found all Audio Logs, alone or with another ODST.
Found 15 Audio Logs, alone or with another ODST.
Found 3 Audio Logs, alone or with another ODST.
Got 15 headshot kills on NMPD HQ.
Got 10 Spartan Laser kills on ONI Alpha Site.
Got 10 Rocket kills on Kizingo Boulevard.
Stunned a vehicle with an overcharged plasma pistol and quickly killed the driver.
Plasma Pistol Overcharged and quickly killed 10 Brutes.
Got 5 sticky grenade kills in any level.
Completed Kizingo Blvd. and unlocked the Mickey character in Firefight.
Traded weapons with a fellow character.
Found the 3rd clue unraveling the mystery, alone or with another ODST.
Found the first Audio Log.
Completed Uplift Reserve and unlocked the Dutch character in Firefight.
Killed all Wraiths in Uplift Reserve.
Completed Tayari Plaza and unlocked the Buck character in Firefight.
Got 10 Needler supercombine kills on any covenant.
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.
Find the final clue unraveling the mystery, alone or with another ODST.
Killing things that are new and different is bad, alone or with another ODST.
Killing things that are new and different is good, alone or with another ODST.
In Firefight, finish a full round without killing a single enemy.
Score over 200,000 points in Firefight on Lost Platoon.
Score over 200,000 points in Firefight on Rally Point.
Score over 200,000 points in Firefight on Security Zone.
Score over 200,000 points in Firefight on Alpha Site.
Score over 200,000 points in Firefight on Windward.
Score over 200,000 points in Firefight on Chasm Ten.
Score over 200,000 points in Firefight on Last Exit.
In Firefight, on any mission, pass the 4th Set on 4-player Heroic LIVE co-op.
Complete Highway on 4-player Legendary LIVE co-op, with Iron, and no 'Hog or Scorpion.