Blockchain digital collectibles. I'm not sure I'd classify it as "cool", but it certainly is interesting. I'm always looking to see what new ideas are gonna revolutionize the world (mostly so I can invest in companies), and digital collectibles is something on many collectors' radar.
The idea of digital collectibles is interesting. The "products" you buy is virtual without a hard copy of it. So instead of a physical hockey/baseball/football/basketball card that you can hold, you'd own it in digital format. You can trade it or play whatever pre-defined games that are developed for it.
As an old school collector that prefers physical products, this doesn't appeal to me too much. That said, it has proven popular so far and does hold potential. The times are certainly changing: