Well, you can man the turret of the phantom. But if you stay on it long enough the effect of "fall time" will come in and kill you. If you don't know what I mean by that, bungie has created a certain...
You cannot actually board a Scarab and drive it like you can with vehicles such as a Warthog, however I have heard of a glitch where on "the Ark" You kill everyone (including Marines) but don't...
There is the "regular" warthog with a .50 calliber machine gun mounted on the back and the Gauss Warthog that fires explosive rounds from a turret on the back.
You can't drive the scarab on regular Xbox, but you can on Xbox Live on Mission 6: The Ark at Rally Point Brovo, What you have to do is run into each corner of the Scarab's Main Computer while...