Horseshoes would probably be pretty confusing, actually. Figuring out sans context that this weird metal crescent was supposed to be nailed onto an animal’s hoof would be a feat on its own, but add on people hanging them up as decoration out of superstition or just, like, throwing them, especially in places where there aren’t any damn horses, that’s really gonna muddy the waters.
My vote’s for either vacuum cleaner attachments or old batteries. I barely know the appropriate uses and contexts for all these vacuum cleaner attachments, some future guy with presumably no foreknowledge of our culture or lifestyle doesn’t stand a chance. And if we’re far enough in the future that no record of our way of life remains, I don’t care how much they keep going and going, those Energizers are gonna be dead, and these archaeologists are gonna all be scratching their heads trying to figure out why we have so many random metal cylinders in all different sizes that are, at best, completely inert, and at worst leaking caustic sludge.
“If these devices were, as previously believed, implements in some sort of ancient ‘throwing game’, I can only assume this to be the result of a misguided attempt to play the sport on horseback or, heaven forbid, to teach the horse to play the game itself. Truly, our ancestors were a primitive people.”