I like the physical, visual representation of data. If done well, it can forever change the way a person thinks about and understands something.
So, I think this keyboard frequency sculpture by Mike Knuepfel is neat. It depicts which keyboard keys are used most frequently, with the height of the key proportional to how often it has been used. I would love to see this sculpture in reverse, with the least-used keys the tallest and the most-used keys creating the deepest indentations.