For myself, as a "Jill of all Trades, master of none," I like the skill set I have.
It would be hard to nail down (HA! No pun intended) a particular single skill, because when it comes to home improvement, there are so many that come into play, and they are all interrelated.
Depending upon the extent of the improvement, if you're going to alter walls, for example, you'd better know something about how to find and deal with plumbing and electrical as well, in case either or both need to be moved.
I can deal with minor electrical and plumbing issues, but when it comes to gas lines, I'm calling in a professional, and the same goes for any major re-wiring that needs to connect to the main input to the home.