Spin recovery.
Good point about knowing the basics.
They stopped requiring private pilots to learn spin recovery. They used to teach it in the 70's but I don't know when they stopped.
You can get an aerobatic certification but It makes you wonder how many fliers have never had to regain control of their aircraft.
Maybe it doesn't matter. Just about all of the local small plane crashes are fuel or mechanical problems. But still, knowing what your plane can and can't do, actually 'feeling' it, seems like a no- brainer to me.