I use the Shimano, bottom of the line, MTB shoe. Performance carries them. Got 'em completely for the price, $35.
Love 'em. I walk around in them all the time. I was in an alleycat once that involved a foot race and they came in real handy then.

I've also heard good things about Specialized brand MTB shoes. Sanoma, I think, is the name. Whatever it is, it's their bottom of the line shoe, but I hear it's very walkable.