Icons Of The Web features a bunch of favicons, with the size of them being proportional to their traffic.
Click on the image above to see more details, and look up your favorite sites to see how they measure up. The sites with the least traffic get icons of 16 x 16 pixels, VGMaps.com gets a better-than-I-expected 48 x 48 pixels. If you want to find it manually, it's under the Yahoo! icon. Not too many cases where I can say "Aw, you know, vgmaps.com is only just under yahoo.com".