My favourite language is C++, although my skills are probably a little out of date. I mainly use Java in industry but I'm not very keen on the direction that it has going recently, specifically the auto-magical Spring.
I mainly use C++ for a framework that I have been developing since 1996 full of different AI techniques and it's about 86,000 lines (or 30,000 semi colons). Every time I come up with a new idea I extend the framework so that I can re-use loads of code. This is mainly a hobby although I have used it for research in academia. I'm starting to focus on the idea of starting a business from my personal research though.
I call the framework HelloWorld