Laser Blaster
From Halopedia, the Halo wiki
Laser Blaster
Laser Blaster is an Achievement in Halo 3: ODST. It is awarded for getting 10 kills with a Spartan Laser during the ONI Alpha Site Campaign mission. It is worth 5 Gamerpoints and is quite easy to do because you start off with a Spartan Laser and later in the level there is another one. The achievement can be done at the beginning of the level as there are 3 Wraiths that net you 3 kills each, leaving you with only one kill to get with your last two shots.[1]
It is represented by a red and silver signpost with a Spartan Laser in front of it.
Sources
http://www.youtube.com/watch?v=p4P7qbt_8lY&feature=related
