Technically all of them, since the pet can wear whatever. But specifically there's the default pet bindings, the rubber bindings, a bitchsuit, and a cat outfit.
Viewing post in Ero Dungeons [Old Version] comments
yeah I'm an idiot and didn't realize that the bindings were changed from weapons to an outfit, I got the adventurer I had as a pet before the cursed weapons overhaul so they were locked in the weapon slot, (back when the standard bindings were the bitchsuit.) I realized this after changing her back to a pet from being forced into a prisoner and realizing that she had a collar as a weapon instead.