Ask HN: How to spend 6 months (personal development)

I've decided to take a break from the job market for half a year to devote some time to personal development. While part of it will undoubtedly be spent exercising, learning to play the piano, biking, meditating and playing video games - a non-trivial chunk of it will be dedicated to professional development. Ideally, I'd like to come out of these 6 months with one or two new marketable skills, but more importantly to hopefully rejuvenate my love for programming as a craft.

To this end, I would love to hear your suggestions & feedback. Anything is fair game - from self study, MOOCs, structured courses - literally anything that can be reasonably accomplished within a 6 month timeframe. I do have some specific areas of interest, but am very open to hearing about others I might not have even considered. For the sake of this thread, budget is not a concern.

My background :

full stack developer w/ 5 years experience, having variously worked on web dev (front, back) & windows desktop applications

Examples :

    * Security - OSCP certification; Coursera MOOC on Software Security or Hardware Security
    * Mobile Dev - Big Nerd Ranch, books & courses
    * Game Dev - Build Unity 3D desktop game(s), presumably mostly self study
    * VR Dev - Unknown

I'm also considering putting together a reading list. Historically, however, I think I've learned best when using books as a reference point to aid in projects and not so much a primary resource. That said, I'm absolutely all ears for tome recommendations as well :)