libwx11

I used this to design a small GUI for my professional work. I had to rename some of the routines in the library to English, so i would understand what i'm doing (couple routines are named in Italian). But after that it was easy to use, comes with lots of example programs, and it looks awesome (check out xsudoky game!) and best of all: It depends only on X11! Any other graphics library nowadays will have a list of 50+ dependencies, but not this one. You may argue it's not portable, X11 may be surpassed by wayland some day blahblah... I don't care. I may be old-fashioned, but to me this is a gem!