A NFT Marketplace like OpenSea to negotiate NFTs. There are not so many features as the real one but it's a proof-of-concept.

A NFT based game. Users can mint NFTs to play the game and each NFT has associated metadata that change as the game goes on.

A DAO (Decentralized Autonomous Organization), which is something like a organization that can administrate itself.

A clone of the already famous NFT Marketplace Open Sea. There are not so many features as the real one but it's a proof-of-concept.