EmuNations

Playnite is an open source video game library manager which supports 3rd party libraries like Steam, GOG, Origin, Battle.net and Uplay. While providing one unified interface for your games, it includes game emulation support, fullscreen mode, themes and much more.

Pureikyubu (formally Dolwin) is an open-source Nintendo GameCube emulator which initially started development in 2004. It went into hiatus but is now active. That said, it's not the most advanced but has interesting features and is able to boot and run some commercial games and demos...

Azahar is an open-source 3DS emulator based on Citra. It was created from the merging of PabloMK7's Citra fork and Lime3DS project, both of which emerged shortly after Citra was taken down. The goal of this project is to be the de-facto platform for future development...