FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
Marvel (mobile) - Turn sketches into prototypes (new iOS & Android apps)
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...
Gomix - The easiest way to build the app or bot of your dreams
TruFont - TruFont is a font-editing application written with Python3, ufoLib, defcon and PyQt5.
Mockup Generator - Create attractive product screenshots with just a few clicks