Scala, I've had a lot of fun with it. You can also try generative and meta-programming using emf/gmf/acceleo maybe some xtext as well. Learning exotic framewo

Scala, I've had a lot of fun with it. You can also try generative and meta-programming using emf/gmf/acceleo maybe some xtext as well. Learning exotic frameworks can be useful/fun as well. Maybe try a different domain like physics, finance, or even buy a fpga and learn some vhdl?