LiteDB

Definition:

LiteDB is an open source no-sql database.

Background:

LiteDB is designed to be a lightweight, cross-platform, local data storage solution. Although it wasn't specifically designed for use with Unity, its mobile-compatible design makes it appealing for many Unity devs looking for a simple way to store data locally.

I have personally used LiteDB in (unreleased) prototypes, and have found it to be easy to use, portable data storage solution. My current (in-progress) project uses it extensively as the backbone of the game's various configurations and its save data systems.

Further Reading:

If you're interested in reading what I have personally written on the topic, you may find these posts useful: