I carry an original Colt #3 (Thuer) derringer, in .41 rimfire, loaded with a newer CBC/Navy Arms cartridge (plus I carry 9 spares). Granted, the .41 RF is no powerhouse, but contrary to popular myth, it is NOT so wimpy that it will bounce off a telephone pole at 15 feet. In fact, it will bury a slug fairly deeply in solid wood at that distance, and is quite capable of inflicting lethal wounds at point-blank range. It is strictly a "face gun" (i.e., you stick it in your target's face and pull the trigger), to be carried when a larger gun would be too indiscrete for carry (I can slip the derringer into a pants pocket and you can't even tell what it is, or hide it in the palm of my hand).