Sanae gets one in episode 6-2 of the anime's second season, when she decides to become the SP (Special Police) for the tentacle-haired object of her obsession. She sets several booby traps in Eiko's room to ward of threats, then steps inside and trips one. This trap comes in the form of an arrow, which she catches just inches away from her head. For such a goofy character that's pretty hardcore.
Any time Chizuru gets angry or has to spring into action.