As for interesting, anything involving quantum mechanics or astronomy goes straight to the top of the list! I’ve been looking for someone to explain quantum post-selection in baby terms for a while now

Useful, well, do things like realistic combat in all its forms fit? The only experience of it I have is from movies and TV, and I wouldn’t trust them with a bag of peanuts. Also, diseases, injuries, and treatment would be good. Oh! And mental health conditions! How to do a good job of writing characters with depression, schizophrenia, anti-social behaviour disorder–you know, all the stuff you see done so badly so often.

And then there’s all the stuff I know nothing about but which no doubt holds some really interesting nuggets. Like geology. Oh, and how the heck do computers work? Like quantum post-selection, I’ve not been able to find a baby-terms explaination that makes sense. As far as I’m aware at the moment, it works something like this: really small transisters > magic > the Interent and Skyrim.

So, erm, that’s a vaguely babbled wish-list. Hope it’s of at least a little use