off the top of my head:
Oracle (READ: aggregated/decentralized APIs feed) services and other infrastructure that supports decentralized protocols (network graph, etc.)
Decentralized lending, borrowing, trading.
SaaS products in on-chain analytics, portfolio management, commerce aggreggation.
Gaming
Fine Art (a tiny minority of the art scene in crypto is pretty interesting, ex. distributed multiplayer run-time art, something that can't really exist outside of the medium)
Digital Collectibles as an end consumer product or in service of the construction of lifestyle brand / gaming / etc startups. (A lot of the most boring use cases land here, imo)
Advertising
Content creation/consumption