Sometimes, when playing Sacred Icon on Heroic, you may find a Brute's corpse near the plug locks, in the area where you fight an Enforcer. When you deactivate the containment shield and the platform you are on begins to move, look at the Brute's eyes. They will occasionally blink.
Sometimes, if you shoot a corpse in the head, say a Human, the eyes will blink. All you need to do is get a weapon; a Battle Rifle or Magnum works well. Kill a Human ally, but make sure the corpse is on its back or its side so you can see its eyes. If the Human is wearing a helmet, shoot it off. Now, simply look at the corpse's eyes and shoot at its head. If you pay close attention, the eyes will blink.