Destroyed vehicles glitch
From Halopedia, the Halo wiki
To get inside of destroyed vehicles, you will need a Spartan Laser. Then, approach a vehicle (preferably a Warthog) and stand next to it (your body must be touching the vehicle). Press RT (Right Trigger), then B to enter/ride/drive on top. Next, charge the Spartan Laser and just as you fire, enter the vehicle. Note that you cannot drive the vehicle.