I wish Rainbow Rocket Giovanni got a keystone back in Gen 7. It's such a shame that he has a mega, yet doesn't have a keystone incorporated in his design. Maybe it could be pinned on his collar, like the Earth Badge in his Yellow artwork (picrel). God his yellow art is so sexy. Alternatively, I could see him wearing his mega stone as a ring, but I'm pretty sure that's already been done by some other trainer.