For an interesting perspective on this topic I recommend this post at Ribbonfarm on "The Calculus of Grit".
Whatever you pick, I recommend also getting good at writing, in particular at explaining clearly and succinctly things that are relatively non-trivial and counter-intuitive. It's rare and valuable in itself; it also eases the job of persuading others that you do rare and valuable things.
Hey everyone I just read this, which in turn lead me to this and I'm curious as to what are some skills and fields of study that people think fit the category of 'rare and valuable'.
Not just in white collar environments either, but also considering the entertainment industry, hospitality, trades and so forth.
I've noticed anything that involves interfacing tends to have good dividends, especially if you can freelance.
Would love to hear your thoughts.