If you don't want to ride around with a mini adjustable wrench from Ace or TrueValue Hardware in your backpack, you can spend $25 for a JethroTule. Surly makes this stainless steel 15mm box wrench with an attached bottle opener. The bottle opener part is drilled, so you can hang the tool from a string loop or put it on your key chain.
The wrench fits the 15mm track nut holding your fixed gear bolt-on wheels to your frame. It has a decent smooth feeling to it, and the back of the bottle opener part is relieved to reduce the weight. The pricey nature has to do with the fact that it is made of stainless steel. Remember you fixie riders: Keep a wrench, tire levers, extra inner tube (or patch kit), and a mini pump on hand this spring riding season. No matter how fly your stylish and minimalistic ride might be, you can't Bungle in the Jungle with a flat tire.
Photos by Wheelgirl.