When it's time to put fear in the hearts of your players on a damage roll...
These are wooden. Obsessive lunatic that I am, I actually rolled them a thousand times and checked that they were sufficiently random for play. I have an all-metal set in my shopping cart ready to buy when I get the urge.
Actually that would be a great raspberry-pi automation project. Throw dice, detect with camera, update probabilty view, collect dice, repeat.