On the level outskirts there is a hidden item at the beginning of the level. when you start the level you will notice a blinking passageway proceed through the passage way and turn directly around and look up and you will notice a light. jump and duck at the same time to get on top the light then turn to your right where you will need to jump and duck one more time to get on the roof. once on top the roof you will find a dark alley way to your left go down that alley and pick up the item as if it were a weapon. This puts you into blind mode, this is where you cant see your targeting reticle health etc. but you can still see what you are doing. This may be the way to unlock something and it might not be the only hidden item.