Personal projects, Racket with gui-easy. Close to frictionless GUI development, very nice language(-platform) to build with. Excellent metaprogramming.
Professionally, Java and JavaFX. Decent multi-platform story, there's a config flag for tuning everything, and there's a library for pretty much anything anyone has ever had an issue with and when they don't fit as well as you'd like you just tear it up with reflection and fix.