Inspired by Q's post here, I thought of some types of refs none of us should ever want to be. And I'll admit it, some of these might be from personal experience. No, I'm not gonna tell which one(s), you'll just have to figure it out on your own. Anyone who knows me at all will probably be able to figure it out.
Suffice it to say, some of these are just observations, not that I've ever worked with any ref like these (though I know they exist). I'm quite pleased about that fact.