Following on the steps of Dotsies, FatFont is a particular kind of type- one that experiments on the graphical representation of numbers. Miguel Nacenta, Uta Hinrichs, and Sheelagh Carpendale from the University of Calgary have created an alternative visual reading of numbers- this is, recognizing a digit by its amount of contrast. So in ascending order, 1 would be the thinnest stroke and 9 the boldest:
Now in the applications of this font is when it gets really interesting. Take this example of a topographic map- the numerical values of the map have been replaced by the new digit character, creating a visual density based on numbers. It's a very impressive experiment that translates numerical data into a graphic value, the result being an 8-bit look-a-like map. You can download the font here.