The runner up (and only due to my massive bias on the eventual winner in this category) is the Pantherella Sock. Pantherella are purveyors of the finest socks and the famous 'Gentleman's Business Sock' exported worldwide as the sock to complete the suit. My favourite Pantherella product is their cashmere socks and for those who haven't worn a pair of cashmere socks, know that the feeling of putting them ON is like the same feeling you have when take OFF your regular socks in bed, but better.
An honourable mention goes to Happy Socks who just create socks that do what they say on the sole!
Check out there recent work with Be@rbrick and some early Sock&Sole work on their Spring/Summer '11 Collection.