I'd say any 1xAAA light that is a clone of the no-longer-made Arc-AAA. The Fenix E01 is one such clone, and a nice light for a cheap price. Many Arc-AAA's tended to develop flicker over time (and not just from dirty contact surfaces). I don't know how the E01 lasts over time. I used a Gerber Tempo 1xAAA on my keychain for quite a while (because I got it on sale for $5). It does not feel like it has the build quality of one of the Arc clones, but the Gerber has never failed and never flickered. A solid performer despite its thinner metal feel.

I see someone else mentioned the Gerber Infinity. I have an Infinity Ultra from back when CMG made them, before Geber bought them out and changed the light somewhat. That's a fantastic low-output long-lasting light that has never failed. But a 1xAA light is too big for a keychain light IMHO. You really need 1xAAA. I don't like the watch battery type keychain lights either. The batteries are too expensive and don't last all that long.

I no longer carry a keychain light. I carry a 4Sevens Quark 1xAA with a 14500 rechargeable lithium ion battery in its small pouch on my belt. Much more versatile (and much more expensive!) than a Fenix E01 if you're willing to give up keychain carry and go for belt carry instead.

For your stated needs, I vote for the Fenix E01.