The CMG Infinity Task Light is a rugged, solid-aluminum-bodied LED flashlight that is small, simple, and reliable. Originally released around the new millenium, and having since been bought out by Gerber, the original Infinity isn't going to knock your socks off with its high output. The truth is, it isn't all that bright at all, but that's not always a disadvantage. As the name implies, it is a task light, and is good for close-up tasks in the dark without blinding you or totally destroying your night-adjusted vision.
CMG Infinity Task Light: Single-AA LED flashlight
Another feature of the light is its simplicity. It doesn't even have a switch, or even a spring, which are often weak points in a flashlight. The body of the flashlight is used as the negative conductor, and the negative battery contact itself is simply a small raised cone-shaped bump at the base of the battery cavity. The light emitter circuitry and LED bulb are housed in the screw-on cap, and the light turns on when the cap is screwed down enough that the battery starts to be squeezed by both the positive and negative contacts, making a consistant connection. Unscrew the cap just a bit, and the battery can no longer reach both contacts, breaking the circuit. Simplicity at it's best! This does cause a bit of battery rattle, but you wouldn't really notice unless you shook the light around.
The cap and body are attached with fine threads that are just loose enough to move easily, while being tight enough that the cap won't turn on its own. There is enough threaded area for 5-6 full turns of the cap, so even if the cap does turn a bit, there's no real danger of it coming completely loose and falling off. The LED is recessed into the cap, which, though it is machined into a hollow cone, doesn't really act as a reflector. The LED itself acts like a lens to direct the light beam.
Also included is a removable pocket clip, and while you probably won't clip the light to your pocket, the clip serves a far more useful purpose: clip it to the bill of your baseball cap, and now you have a hands-free headlight!
The light runs on a single AA battery, and is advertised to run 41 hours on an alkaline battery. Your mileage may vary, of course, because no two batteries are identical, but the claim is is fairly accurate: it takes nearly two days of constant use to run down a new Duracell.
CMG Infinity Task Light and a Spyderco Ladybug
A couple of years after the original CMG Infinity was released, a new Infinity Ultra was released. This version features a brighter LED with the trade-off of lowering run-time to 25 hours per battery. In the mid 2000's, Gerber bought the design and began producing their own versions of the lights, and now make an updated version of the Infinity Ultra with a longer runtime of up to 60 hours even with much brighter output than the original CMG Infinity. The body has changed slightly, but the lights are functionally the same, and still very popular. If you are looking for a small, rugged light that uses common, easily-obtained batteries, and don't mind the relatively low output, take a look at Gerber's Infinity Ultra Task Light.