Here's a pen from Sega World London. As you can see, the pen itself isn't Sonic themed (Just silver foil with black spiral) but the base is. It has speeding Sonic and Segaworld in silver. The pen is rather large, so it's mostly decorative. Why? It appears to be one of those 'floating' pens, where it will hover in place over its magnetic base. It is probably spiral designed so it looks fun when you spin it.