The only weapon I carry with me is my common sense. There's a 2 mile stretch of my morning commute through a very poorly lit neighborhood, means no street lights what so ever. I always take the middle of the road in these parts to give me some reaction time if anyone ever decides to jump me from the side.

Unfortunately for us cyclists it is very easy for someone someone to knock us down who has intention to do so. The only way your 9 mm can make a difference is if you have it out and already pointed at the general direction of your attacker. A senario that is very unlikely to happen.