ODST Firefight has a Vehicle Set option that lets you change what vehicles spawn on the map for Lost Platoon, including the Gauss Warthog, Scorpion, AA Wraith, and Hornet.
Halo: Reach should have the same option, letting players choose between the standard Warthog, Gauss Hog, Rocket Hog, Scorpion, Falcon, Ghost, Revenant, Wraith, and Banshee.