I wouldn't have believed this if I hadn't just seen it: working in a building owned by a friend, I saw floors--finished interior ones--made of OSB.
That's right, oriented strand board; you know, that underlayment stuff that's so ugly nobody in their right mind would consider it for finished work, right? Except that when it's sanded and varnished, it looks really nice.
I don't know if this is something that's even been published anywhere, possibly in some architectural magazine or other; the architect who remodeled my friend's building suggested it. It was installed more than a decade ago and has stood up to wear pretty damn well.