Maybe not ultralight, but certainly ultra-cool – and you can cut a banana with them!
91 grams. US $60 (May 2019)
‘No more frayed edges, stains, or fading: if cared for correctly, carbon fiber playing cards can last a lifetime. Made from 100 percent carbon fiber, these thin and durable cards have a twill pattern and a matte surface. In case things get a little rowdy during gameplay (it happens), they’re waterproof as well. Spades and clubs have crisp white faces; hearts and diamonds are styled in striking red.’
From XC Carbon who have a heap of other neat carbon fibre goodies – eg tubing just in case you wanted to make your own hiking poles, pack frame (or something)