When you're commuting to work by bike, the last thing you want are grease stains on your nice pants. Avoid that with the SKS Chainboard. Easily adaptable to just about any bike, it'll keep your legs stain-free. Unlike other chainguards, it's made of plastic and has hollow elements, keeping it relatively lightweight while still looking attractive when installed.

SKS Chainboard
Buy It Now from Bike Somewhere, $25