Here's my list off the top of my head. This is with the caveat that I'm always willing to learn the tools needed to do a job that someone is paying me for.
-Ruby on Rails: I know Python and have experience with several Python web frameworks, so I don't feel like it's as useful to learn another language and framework with a feature set that's so similar. I'd rather focus on new paradigms
-Windows based development: At this point, I'm happy on my mac, and if I ever move, it'll probably be to Ubuntu.
-Graphic Design: I'm visually impaired, so focussing time on this would really not be playing to my strength. I love knowing the basics of how to make a webpage that looks reasonably nice, but you'll never see Adobe Creative Cloud on my credit card statement.
-More Java than I already know
There's also a lot of stuff that I'm somewhat interested in, and will read an article on if I come across it, but don't take an active role in learning more about it. This is stuff like game development, non-web related security, hardware, ...
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