I found Crystal some years ago. Due to installation issues, I couldn't use it for long; compiler bugs, not upgradable, etc.. Just recently I stumbled upon it again and this time, it works super (at least on my Linux VM; can't install it on macOS Sierra 10.12 beta3 currently). Crystal is like Ruby but with types (mostly hidden) and super fast because it bases on LLVM. I still love the Ruby syntax; I started Node.js only because of CoffeeScript. Crystal is amazing; this is what I want to learn and master this year for sure.
The other language I find interesting is Julia. I can't say much about it yet because I have only watched some conf talks on Youtube. But it's definitely on my list.
Facebook 's Reason looks interesting to me.