Here's a list of ones i like just my opinion. I am leaving out ARC since it's no longer made, and If you find one,
it's just too expensive for what it does....
COIN CELL LIGHTS:
Photon freedom
PT eclipse
Streamlight keymate
STD BATTERY(AA,AAA)
Cmg/gerber Sonic (I like the CMG older ones better)
Gerber/CMG/ultra-G: infinity ultra
Dorcy: 1AAA
Couple of notes,,,
many feel the infinity ultra is a little big, same with the dorcy.Just depend's on personal preference
The sonic has fan's and detractor's, some of the sonic's turn too easy and come on in a pocket, I have not had that problem, but some do.( I think it has to do with how you carry the keys, loose pocket no prob, but in tight jeans pocket i can see that)
there is the peak light's, really nice,well made but i never
owned one.
Someone will inevitably bring up how the long gone ARC is best, and as a total unit it might well be. But if you don't want to spend 50-100 bucks for a 25 dollar light look elsewhere. there are light's in my list as good or better then the arc/aaa as far as beam and brightness goes. (a photon freedom, a sonic if you get a good bright one, same for the dorcy).
Also a modded mag solitaire is a great light, (see flashlight review's.com for ideas)I carry a modded "easy mod" and like it a lot, but lately it's been a photon freedom in night vison green. VDG