Loads of people on the STW Commuter Club thread have told us what they ride to work and I've been surprised at just how many (most it seems) ride singlespeeds rather than MTBs. So show us what you ride and why.
I'll start with my current commuter, a real heavyweight, 1994 Specialized Hardrock with random spare parts from the garage thrown on. It's an absolute pig to lug up the hills and I'm in 2 minds whether to swap it in for a CX or RoatRat style bike or just treat it as resistance training. I think I would enjoy something light and purposeful a bit more.