Rare and Valuable skills worth mastering?

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.

Not an answer to your question, but I recently realized that all skills supplied by the standard curriculum of modern education were by definition oversupplied and therefore nearly worthless. "Study anything that other people don't" is probably not a bad heuristic.

Custom furniture-making, custom boatbuilding. Starting successful technology startups. Running the front-end of a fancy restaurant. Being some sort of "personal consultant."

The rare skills and knowledge that are directly applicable to your own life through being a human. Medicine, fitness, sex, motivation, rationality. The more money you have, the more you can farm things out, but you're still left with the problem of judging which farmer to employ, which requires some knowledge on your part.

Basic public speaking skills are always valuable, even at the lower level, but the ability to speak really well is rare and valuable. The same principle applies to writing well -- it shouldn't be as rare a skill as it is, but it's always worth improving.

A good knowledge of accounting and taxes tends to be useful in a lot of areas.

For most people, knowledge of how to cook won't directly be part of your career, but these days, it's a valuable social skill, maybe especially for males. As Robert Rodriguez has said, you gotta eat the rest of your life, you might as well know how.

I'm reminded of Heinlein:

A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.

Personally, I've never planned an invasion, and I'm not going to start now. Also, changing diapers is a lot easier with modern disposables. Hardly a skill at all.