I noticed the new-ish Nicron N81 flashlight can run on run on a single 18650, 14500, or alkaline AA battery. But I haven’t found any reviews on that light. Can anyone else recommend a light can run on all 3 of those battery types? Not sure about the N81, but I would prefer if the flashlight could use an unprotected 18650 (without fear of fire, etc). Thanks…
You could build an S2 with a 17mm boost driver that would run on any of those, but the problem is physically fitting them into the light. That Nicron uses an adapter to make the 14500/AA batteries fit. 18650 and 14500 as easy since it’s the same voltage. Normal AAs will require a boost driver though, and there are very few options.
There was some light (forgot which, or who made it; someone jump in if you remember what) that could run from Li cells or even a D-cell (at much-reduced brightness, of course), but I don’t think I’ve seen one (or the appeal) of being able to run from an 18650 down to an AA alkaleak.
The latter is so low-drain that you’d be better off with a dedicated AA light that could at least wring it dry. Almost every dual-chemistry light I have will refuse to turn on if the alkaleak is even only half-spent. Even my 2-cell SF13 (?) goes mental if the cells are too spent. It’ll turn on for a while, blink a few times, then unceremoniously shut off.
And you’d still need a physical adapter to go from 18650 down to 14500, not just a sleeve.
If anyone makes such a light, hey, great, but I haven’t seen any.
Thanks for the responses guys. It sounds like my requirement/desire is a bit niche. 
For the record I would only plan to use AAs in the light in a pinch (like during a long backpacking trip or an extended power outage). I might just get the N81 even though it is a zoomie (which means more optical losses). I attempted to contact the manufacturer in hopes they might give me one as a sample in return for reviewing it. I have yet to find anyone who has written about it.
I think this izz da one……. http://www.lumintop.com/sd4a.html
The BLF Lumintop SD10. I ran mine in tests on nearly everything, ( with some custom adapters) including AAA, AA, C, D, 10440, 14500, 18650, 26650, 32650, CR123, and it even lit up on low with a CR2032 coin cell.
Jetbeam WL-S1
According specs works with 1 x CR123A, 1 x 16340, 2 x CR123A, 2 x 16340, 1 x 18650 and 1 x AA.
BTW, Sofirn SP33 works with 3xAAA(with adapter), 1x18650, 1x26650, 1x21700 and 2xCR123
BINGO!..that’s it … I couldn’t remember model number
There ya go…
I have 3D printed adapters to run 14500’s in place of 18650’s, since the Voltage is generally the same, these work great. AA’s will also work if the light will run on the lower Voltage of an AA, which most will not.
For 2 and 3D cell lights, I printed adapters that will run in addition to the original D cells, 2 or 3 AAA’s, AA’s, and C’s along with single 14500’s, 16340’s/CR123A’s and 18650’s. The same cells (except for the D’s) can be run in a 2-3C cell LED light.
Looks like neither of those lights (SD4A or SD10) are still in production. Both looked pretty neat — but seem kind of pricey (at $60). Thanks again to everyone…
It may be possible to find a used one here on BLF, as sometimes randomly they do go up for sale. (if looking for a used one at a good used price maybe post a want-to-buy thread.
The old BLF Lumintop SD10 will take the variety of batteries you mentioned.
The SD4A on the other hand does everything except XX650 sized batteries. Lumintop advertised that the SD4A would run XX650 length batteries with the optional body/tube but the body was never actually released. Nonetheless it is pretty incredible that it actually runs on everything from 1xAA upwards with the appropriate spacers.
I would rather not go the used route when it comes to electronics — especially when a new option is available. I will probably pull the trigger on the Nicron N81 this weekend.