Grunt captain. Looks similar to the grunt, but has hair and is a little tougher. Different grunt captains may carry different weapons.
Super Guards - Superguards wear black facemasks and black/silver armor. They only carry chainguns and can take practically a full clip of pistol ammo to the head. Watch out for these guns, as if you can't stun them with repeated shots to the head their chaingun will devastate your armor.