How about the old cowboy guns of the old west? I belong to an organization called the Single Action Shooting Society or SASS which is all about the guns that the cowboys of the old west used, from lever action rifles and break open shotguns to single action six shooter pistols. I would think the main disadvantage of a single action handgun is that it has to be cocked each time its fired, but hopefully if used properly it can be just as effective as any other gun in self defense.