Using an ultra-wide fisheye lens(?), Flickr user heiwa4126 has taken some really crazy images of Tokyo and its surrounding environs. His equipment includes a Nikon D80 SLR camera and the aforementioned Sigma 8mm fisheye lens. Other than that, I don't know much about it and I'm disinclined to investigate further at this point. Just appreciate the radness and look at the pretty pictures.
Check out the rest of the images (about 100) here.