Look mom, no wires - Streamlight TLR-1 HL CR123A LED Rail-Mounted Tactical Flashlight

Besides being obviously REALLY BRIGHT (Hint: DO NOT be facing a mirror when testing it), it is a very simple mount using a spring loaded, self containing, wing screw (meaning it will not fall out, and does not require tools), it will mount on the dust cover of any pistol that has the short picatinny rail, or it will mount on a rifle, also to a picatinny rail, so it can be switched from pistol to rifle in just a few seconds. I mounted this on a AL (Armalite Lefty) quad rail, making it easily activated using the forward hand, light on opposite side of hand, however in this position, the switch can be put into position to receive a hard hit, and possibly damaged, so I used a MagPul short hand stop up to the back of the switch, so when laying the rifle on it's side, hand stop help to keep pressure off the switch, thus protects it from most potential damage.