GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Python - Python is a clear and powerful object-oriented programming language, comparable to Perl, Ruby, Scheme, or Java.
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.
Java - A concurrent, class-based, object-oriented, language specifically designed to have as few implementation dependencies as possible
JavaFX - JavaFX is the next step in the evolution of Java as a rich client platform.
Rust - A safe, concurrent, practical language