In Halo series games CPU characters never run out of ammo. If you hand them a weapon that has full ammo and then you need that weapon later it will still have full ammo. This trick is particularly helpful when it comes to the Battle Rifle, Covenant Carbine, Rocket Launcher, Fuel Rod Cannon, and shotgun because most CPUs carry either the pistol or the standard Assault rifle. An extention of this glitch is to hand a CPU a Rocket Launcher/Fuel Rod Cannon and then get them to sit in the passenger seat of a vehicle. This makes it easier to deal with other vehicles and armoured units.