Sicherman dice have the same probability distribution as normal dice but they have an interesting numbering pattern. Instead of the standard 1-2-3-4-5-6, one of the dice shows the numbers 1-2-2-3-3-4 and the other die shows 1-3-4-5-6-8.
An example of the dice, and the associated probability tables, can be found at cut-the-knot.org.
These dice are useful for a variety of educational and gaming purposes. Or get creative and come up with some new and unique dice games of your own!