c-rings.
Pretty please. It's so rare that anyone REALLY uses them, and since they can't be picked up by the vacuum and they sell for nothing... it's just ground clutter for the sake of ground clutter at this point.
EDIT - or get rid of everything but unique rings entirely. It's a useless slot that means nothing unless there's a unique in it and since it can't be vacuumed like normal 1-5 loot, there's no real need for the 'upgrade as you level' system.