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" use for which it is intended.

Run time, a primary consideration for a light used often, but generally forgotten when not in use, is, I believe, a paramount concern. With an alkaline battery the E-01 is reported at ~20+ hours. Mine is loaded with a disposable lithium battery, I've had it and used it for over 2 years.

If you could live with a bigger, somewahat dimer ( but still plenty adequate) light, I'd go with a Gerber Infinity AA. With a bit of tin foil, it gives you the ability to use AAA, as well.