I’ve seen plectrums – or picks, as they are more commonly known – made of plastic, metal, even felt – but the Obsidian Arrowhead Guitar Pick is made of volcanic rock. These picks were created by Seth Maranuk. A piece of obsidian, a glass-like material formed in rapidly cooled lava, is hand-shaped into the arrowhead shape for a good grip. The glass is said to give a “unique sound to your strumming.” The Obsidian Arrowhead Guitar Pick is $20 at UncommonGoods.