for an urban situation today, using public transportation or on foot, I would look to..
athletic shoes not associated with a gang
a gray "hoodie" or dark hooded wind breaker depending on season
dark ball cap without logo
wrap around sun glasses
backpack
The only thing I wonder about are things like the G20 and Occupy movements. This attire sounds a little like the black-whatever-they're-called that ramped things up there. Dark clothes could be mistaken by the police as the clothes of a professional, radical protester. I'm more inclined to go with earth-toned browns and greens.
That said, the older I get, the less inclined I am to spend time in cities, especially big ones. I like to hope that, with this in mind, if the worst does happen, I'll want to be found not camoflauged.
All that said, my trunk's loaded with gear that's kept out of sigh unlese the trunk is open. If anyone does ask about it or the bag under my desk, a great answer is "I'm a Scout Leader."