Kittentools
A set of tools that Catlard Studios uses to make games. Showcases an MVC structure in Unity, and provides many tools for dealing with common 2D game problems. Clone it on bitbucket!
Highscores Plugin
Lucentian provides a multi-platform high score service (free, after 30 seconds of cryptomining). Catlard Studios maintains the unity plugin for integrating this service into your projects. It is open source. You can create your own table and then download the plugin. The video on this page will teach you how to integrate it into your project. Although the project on the repo uses unity 2019, the code files will work with any version of Unity after version 5.6.