You need to find a review written by an enthusiast with measuring, or at least estimating equipment. Assume all the *fire brands are outright lying. Cheap stuff claiming more than about 1500 lumens per 18650 is usually lying. There is, however a pocketable, $40 flashlight that makes an honest 4000+ lumens on a single 18650: the Emisar D4. There's a catch though: it's dissipating about 80 watts of power to do that and thermal throttling kicks in after a few seconds. To give it more HN cred, it has an open source firmware.

As to your request, a couple general recommendations first: skip the zoom, and don't chase output numbers. Zoom is pretty optically inefficient, and small zoomable flashlights don't end up with much more throw distance than similar size fixed reflector flashlights. They don't do wide-angle illumination as well either. A good reflector with sufficient output provides both at once. As for brightness, human perception of brightness is roughly logarithmic (with a base between 2 and 3), so it takes four times the output to look twice as bright. Anything over about 500 in a pocketable flashlight is pretty decent, and most 18650 lights have more.

Specific recommendation: the Wowtac/Atactical (both names show up on Amazon sometimes) A2. This is one of the smallest 18650 lights, has shortcuts to low, high and last-used modes from off and has a right-angle configuration that works equally well handheld of as a headlamp. A pocket clip, headband and 18650 battery with built-in USB charging port are included. It costs $20, and I have no idea how they make a profit given all the stuff it comes with. Go with the neutral white tint if you can find it; this looks more like sunlight and won't wash out colors as much as the cool white.

Any way to buy off Aliexpress without getting fakes?

A few of the budget brands like Convoy, Eagle Eye, and Maxtoch have official Aliexpress stores. I'm not sure about linking Aliexpress here, as the filter might think I sold my account to a spambot, but their store IDs are:

* Convoy: 330416

* Eagle Eye: 1735126

* Maxtoch: 314381

All three make good stuff that has been popular with flashlight geeks. Convoys with "new firmware" or "Biscotti" have an open source firmware: http://bazaar.launchpad.net/~toykeeper/flashlight-firmware/t...

Forgive me for my ignorance, but why do I need my flashlight to have open firmware?

This is Hacker News. Open source is generally appreciated here even when there isn't a direct, concrete benefit to most end users.

But if you're here, there's a good chance you're the sort of person who could get an AVR programmer and tweak something if you don't like it. Different modes? Timed stepdowns to prevent overheating or not, or more sophisticated thermal regulation for the attiny25 based drivers that have a temperature sensor? A firmware with completely different behavior like near-continuous ramping instead of fixed modes?

It's hackable, and hackable is good.

Any thoughts on the Wowtac A2 vs Wowtac A2S?

The A2S is not worth a 50% price increase for most users, but if you really want more output (in the form of a bigger hotspot, probably not more intensity or throw distance), it's only $10 extra.