Shotty

Shotty was an ODST with a shotgun who aided Johnny and Arby in their assault on the Ark. He was deployed into a combat zone with the Spartan during the attack on the Citadel, and he cleared out several Covvies from the landing zone to allow more Pelicans to arrive. Despite (for some reason) wanting to ride in the back seat of a Mongoose, Arby put him in the turret of a Warthog and put Fred in the side seat.

Shotty helped push on through to the Covenant-controlled shield tower and took down several Prowlers and a Wraith before guarding the tower itself. Once the tower had been taken down he followed the gang back to the Hornets and helped destroy a load more Covenant before getting dropped off on the Third Tower and being picked up by a Pelican.

Some accounts say he was killed at several points during the battle, be it at the hands of the Wraith, during the Hornet flight or during the battle for the Third Tower. Where these ludicrous reports come from is unknown, but the UNSC has officially erased them from record.