Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
Coherent GT - Fast user interface runtime for PC and Consoles
wxWidgets - wxWidgets: Cross-Platform GUI Library
Sciter - Embeddable HTML/CSS/script engine
FLTK - Fast Light Toolkit - Fast Light Toolkit (FLTK)
Electron - Build cross platform desktop apps with web technologies