Basically will take any battery you can fit inside
...except for 4.2V 16340 / 14500 cells. I point that out only because it's a very important point and one that many have historically found confusing, for whatever reason. The higher performance available using CR123A can also be realized by using LFP16340s for a secondary (rechargeable) solution at the expense of some run time. For that reason, this is what I keep in mine most of the time.
Outside the spec, I understand from others that one can finesse a AAA into it (although I haven't bothered to try it), and while that would be sub-optimal from a performance standpoint, it could save the day in a jam, and at lower output levels would probably still be useful.
My favorite is the ProTac 1L AA. It's a very versatile little flashlight.
Same here. It is without question the highest quality / best engineered AA-capable light I own (or know of for that matter), and for me offers the best package of design features and operating scheme. It is unquestionably the 'AA' light I would grab first when it really 'matters'.
Also, don't forget the venerable EagTac D25A. The basic design has been around a long time, but there are very good reasons for that, and in its current (MKII) version, is still a good choice in many respects. It's not 'perfect' (and what is?), but has a feature set / operating characteristics that most find very flexible / usable and easy to adapt to. I have several, and it is the AA light I use most daily 'around the house'. This one
can indeed use 'standard' 4.2V 14500s to some advantage (which I do). It's also available from stock from a
fine U.S. distributor, and is currently in stock with a choice of several emitters, including SST20 4000K R9080, which is probably my most-used (with a 219C example not far behind), although the latter is not currently in stock.
