When you are using a melee attack button for a shotgun, or for a rifle of any type, the kick butt does no damage. In fact, there is no even impact on a target, just a free swing. This bug presents in any version of CoF, and it's really annoying, when you out of ammo and can't even kick an attacking monster. And you can't break any breakable obstacle on your way by this kick too, so you have to switch to another weapon everytime.