Red Skull Pins
Red Skull pins are the pins used by Megumi Kitaniji to take over control of Shibuya. They even seem to work on Reapers, although they don't work on Neku or Beat, supposedly because of their Player Pins. As Neku demonstrates when he saves Shiki from her pin, they can be physically destroyed.
Related ThreadsSome questions on the Red Skull Pin (spoilers) - last post by @ Feb 21, 2014
O-Pin/Red Skull Pins (May Contain Spoilers) - last post by @ Jun 20, 2013