Grunt Aerobics

If you grab the Banshee earlier in Assault on the Control Room (See Early Banshee), you can finish the level without having to open those big doors at the end, and fighting the hordes of Covenant! Just park your banshee backwards so that the front is faceing toward the ramp leading to the top and once it is backed up against the door as far as it will go, press X to get out. It should push you through the door and all the enemies will be frozen, since the door was never opened. The only things that move are little circles of Grunts that jump up and down in sync, one after the other! This might take a while to get right, but it is totally worth being able to melee a Zealot in the back unopposed! This strange grunt behavior can be witnessed in the Pillar of Autumn level on any difficulty, when you reach the point that there is a long hallway with a couple of grunts at the end ( it has some Bumblebee life boat docks at the side). Take out your pistol and zoom in on them, BUT DON'T SHOOT THEM, as they will start jumping in the same way as in the 5th level.

You can also do this with a Ghost by strafing to the right towards the door and getting out of the Ghost so that you are out just before it hits the door.