Shared append only, very slow database. It’s a very specific setup but maybe there’s some scenario for it.
It could be useful for professional licenses, too. Everyone could have a verifiable history of someone's professional license - when it was issued, when it was revoked, again mathematically verifiable. You could be sure that someone's record was never changed or deleted without leaving an audit trail.
Though to be fair, the important part of this is the chain of cryptographically signed and timestamped events. It could work without strictly being a blockchain. You could imagine something that behaves more like a git repository with a flat file database in it.