Gcube has a self-explanatory name. The emulator is designed for GameCube. It is given as an open source and it is available for free. However, the last version was released in 2004, so the support has obviously been discontinued. But then, the program is still widely available and works with no major issues. Unlike other emulators on the market, this one has been created with the one and only purpose to run at least one commercial game at the highest standards. It has not been updated to run commercial games though, so it is mostly aimed at homebrew applications.
The emulator runs on Windows, Linux and Mac OS X. There were a few attempts to continue its ascension – even under different names, yet they have also been discontinued. While Gcube failed on its initial purpose, it has successfully managed to run homebrew applications and this is what it gained popularity for.