How to sew - not just for repairing clothes, but also for the eventual necessity when there aren't any surgeons left after the resource wars.
Keeping your basic first aid skills up to date with courses is genuinely worth every penny you spend on it.
How to tie a simple set of knots - fig 8 and bowline for making loops, also a clove hitch and a reef knot for attaching two lines together are solid starting points
Also knowing what to have in an emergency kit and how to not freeze to death if the heating goes out are very important