My most reliable EDC light has been the small photon light which has been on my keychain for well over 15 years and is still going strong (I'm not even sure I've ever change batteries but it is hardly ever used.)

I have since added an Quark Mini AA which is LESS reliable. Known issues:
1. uses AA. If I keep alkalines in it, the AA cell can leak and cause problems.
2. the head is screwed in and ISthe switch. The head is then loose and can fall off.
3. the head sometimes tightens up and I unknowingly end up with a dead AA.

The solution to the first one is to switch to lithium AA.

The solution to 2&3 is harder to figure out. Possible solutions:

1. keep things as they are. The head and the AA fall off inside my hip pocket.
2. tighten the head with the AA backwards or with a small bit of electrical tape.

Neither solution is satisfactory. I will eventually loose the head and fumbling around in the dark trying to turn on my light is not my idea of fun.

I am considering switching EDC single AA lights. I am considering a zebralight SC52w (if it ever comes off backorder).

Any other options (different single AA light) or ideas (change the way I carry the current light)?