I like AA for headlamps! I have a couple of somewhat older Fenix headlamps that use a single AA, great light.

1AA is probably the best small headlamp format, though a lot of them are heavier than necessary. I just edited my post above to link a review of the Nitecore I mentioned.

Fenix currently doesn't seem to make any 1AA lights, oh well.

Think everyone should have at least 1 AA light, just because of battery availablity.

Still have the Acebeam H16 mentioned earlier in this thread IIRC.

Though if had to buy another think I'd try a Wurkkos HD12

https://wurkkos.com/products/wurkkos-hd1...ariantsId=12322

The Acebeam looks nice! My main complaint with the HD12 is that it is kind of heavy, 48g without the battery or strap. More like 90g including everything. The Acebeam is lighter, and if you want just a flashlight instead of a headlamp, the Skilhunt E2A is quite light.

For headlamps the Nitecore HA11 (mentioned) and HA15 (not sure what the significant differences are) are the lightest out there. The HD15 is a few grams heavier than the HA11.

Acebeam H40 also looks interesting.

Added: the HD12 claims to have reverse charging (you can transfer juice from the flashlight to your phone). IDK if it has been tested. It's pretty marginal since the 14500 battery is so small, but maybe it could let you make an emergency call if your phone was dead.