I found a new walking angle when carrying the big guns. (machine turret, plasma turret, flame thrower, missile pod)
Pick it up, try moving forward while holding up-left. (not dead straight, not directly to the side)
Work with it, try it. Master Chief will bust bunnies.
I was helping my brother with Skulls yesterday and I found the sweet spot ... he was like, "wtf, your guy is hauling ass".