An interesting visualization over at Nmap.org shows the favicons of the 300,000 biggest websites on the Internet (according to Alexa), with the size of the favicons corresponding to sites with the most traffic.
The data has been gathered through a "large-scale scan of the top million websites," performed in "early 2010" using the Nmap Security Scanner, a powerful network scanning tool used by many online security professionals.
The smallest icons, explain the folks from Nmap, correspond to sites with approximately 0.0001% reach, and rescaled to 16x16 pixels. The largest icon belongs to Google, and it's 11,936 x 11,936 pixels large; for comparison, Mashable's favicon (located below and to the left of Facebook) is 640 × 640 pixels large. Of course, to explain Google's icon in its full size, you need to check out the zoom-enabled, interactive version.
The visualization is also available as a humongous poster, available here.