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.
SDL - Simple DirectMedia Layer is a cross-platform multimedia library designed to provide low level...
wxWidgets - wxWidgets: Cross-Platform GUI Library
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
FLTK - Fast Light Toolkit - Fast Light Toolkit (FLTK)
Unity - The multiplatform game creation tools for everyone.