A lot of mine have been covered here already, so I’ll keep it to Drawing.
No matter where you’re at — even if you can only draw stick figures — working on drawing skills is an incredible, compounding investment that pays continual dividends.
Most relevant here on HN I think would be the ability to communicate and articulate ideas very quickly and efficiently. I say dividends because while you can get rusty, the skill never really goes away; I constantly feel grateful for all the time I’ve put into improving my drawing skills over the years.
“Drawing on the Right Side of the Brain” is the book I typically recommend for anyone at any skill level.
No matter where you’re at — even if you can only draw stick figures — working on drawing skills is an incredible, compounding investment that pays continual dividends.