A cork mirror.
I started with a cork yoga block from REI (and a small mirror and wire from Michaels).
I cut a part off using the Miter saw for the approximate size I wanted. I then drew lines to make a rectangular pyramid shape.
The piece was too thick for the bandsaw initially so sawed it to fit.
I bandsawed it, then sanded down the faces with the sander. I was trying to get the top flat but I couldn't manage. I lost about an inch of material because I kept trying to correct it.
I then hand sanded it to make the top a little more flat, then I sawed a slit for the mirror.
A variation of the wire: