I picked up some large hickory nuts when I was walking a week or two ago. With the husks off, they're about the size of a small walnut. I don't know what kind they are but I had to whack them pretty hard with hammer to crack them open. There's some smaller ones in the picture too that were off of a different tree.
We have at least three hickory trees on our lot but they're not big enough to produce. I picked these up off the side of the road.
I'm still waiting on my pecans. The husks haven't started splitting open yet.