Materia (formerly Flat-Plat) is a Material Design theme for GNOME/GTK+ based desktop environments.
It supports GTK+ 3, GTK+ 2, GNOME Shell, Budgie, Cinnamon, MATE, Unity, LightDM, GDM, Chrome theme, etc.
Also Materia has compatibility with oomox theme designer.
Ranked in these QuestionsQuestion Ranking
Pro Customizable via Oomox app
Users can build completely personal version easily using Oomox Gui app.
Pro Under continuous active development
Responsive and helpful developer.
Pro Good support for various DEs
Includes support for Gnome Shell, has a Cinnamon desktop theme, plus supports XFCE, Mate and all the usual suspects.