Funnily enough, in my experience, pecans are the most noticeable and easy to harvest with primitive tools.
I stayed at a place that had probably thirty trees and the floor was littered with pecans, most in a shell, some not, and many were easily able to be snapped open, or of course banged with a rock.
Cashews, while I love them, are literally related to poison ivy and are dangerous to harvest unless you know what you're doing, just as I believe peanuts can be as well.