My wife wanted a cute way to display her plushies on the wall and I wanted a way to not mount a bunch of shelves that needed to be leveled and have drywall anchors drilled into the wall, so I designed a simple set of hex-shaped, cube-style shelves that could be held up with a single nail. My favorite nails for this purpose are called Deconails. 

There are two versions of this model. The first has the mounting tab on the inside of the top wall, but I think that puts too much outward pressure on the shelf and I wanted a way to ensure they could be lined up without too much difficulty. So, I made a version 2, which puts the mounting tab on outside of the top wall and left a slot on the bottom wall so the tab of the shelf below could fit inside the shelf above it.

I've put both models here to give you the choice but I recommend version 2. Also, if you're going to stack them like I did, don't be a doofus like I was. Mount the bottom shelves first and then stack upward. It's a lot easier that way.