Firefight: Lost Platoon

From Halopedia, the Halo wiki

Firefight: Lost Platoon

Firefight: Lost Platoon is an achievement in Halo 3: ODST. It is awarded for scoring over 200,000 points during a match of Firefight on the map Lost Platoon. It is worth 10 Gamerscore.[1]

This is probably the easiest Firefight achievement, as all you have to do is highjack a Chopper early in the game and score kills until you get 200,000 points. It is done best on Normal difficulty.

When doing this on single player, allow a minimum of 2 hours to reach the 200,000 points.