Friends, if we are talking about a small,basic, nearly indestructible, AAA, hard use key chain light, the winner , IMO, is the Fenix E-01., at $11. 13 lumens is more than enough for any keychain light and "find the keyhole or light my way out of the darkened stairway" ... With an alkaline battery the E-01 is reported at ~20+ hours.
Acropolis5 makes good points.
My EDC AAA light was nearly twice that price - a $20 (Amazon) twisty
Olight i3S (20/80/0.5) lumens for ( 8 hr / 35 min / 60 hrs),
(review here), similar to Hikermor's Fenix LD01 twisty (72/3) lumens for (1.5/20) hours.
I think acropolis5 is correct that the cheaper, fixed output Fenix E-01 is a more practical choice than my Olight - 90% of my use is in the (default) 20 lumen mode, and I expect 13 lumens would work just as well, in which case the 20 hr Fenix E-01 battery life (and half the cost) is a winner.
I do like the flexibility of having the high-power mode on tap, though, and the "moonlight" mode is superb for coming to bed late without waking my wife.
My other EDC light is a 4.5 lumen, 12 hr coincell "squeeze on" Doug Ritter Photon Freedom keylight with the "covert" beam shield. I got the Olight because sometimes the Photon would turn on in my pocket and drain the battery (though it is working fine now – hmmm.). Hikermor's suggestion of carrying a spare battery might have been a help there, though changing the Photon battery in the dark would be daunting.
I don't think the "where did I put that?" yellow Doug Ritter Photon version is still available, but you can get the same light in black/white/pink from the
manufacturer or retailers.
The Photon comes with a magnetic cap clip for hands-free use as a cap light or lantern.
Looking back at this - I think I'm a sucker for gadgets, and the manufacturers have my number ...