DR-designed eGear Pico. 10 lumens, 15 hours, single-mode, tiny, twisty, it has everything you ask for except expense: available for $10 locally. I have several attached to all different kinds of gear as a failsafe light source.

My favorite is still the Maratac AAA from Countycomm. I use a fishing swivel to work-around the funky keyring attachment clip, no problems or wear in over 2 years. The ITP A3 EOS Upgrade is the same light with a better keyring attachment, though you can't tail-stand the ITP.
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2010 Jeep JKU Rubicon | 35" KM2 & 4" Lift | Skids | Winch | Recovery Gear | More ...
'13 Wheeling: 8 Camping: 6 | "The trail was rated 5+ and our rigs were -1" -Evan@LIORClub