Small $0.99 flashlight from ebay.
Single LED.
ON/OFF switch at the back. It might be weakest point of this flashlight - it clicks nicely but light gets wobbly if it is touched when powered on. Because of this rubber cap flashlight has also some problems with standing on its back.
This works with single 18650 AA cell - I've tested it Eneloop (as I have few of them laying around anyway).
While this flashlight is often advertised as "3W" it consumes roughly 0.2A from 1.3V Eneloop (260mW).
Emitted light is cold. I don't have point of reference but given the small flashlight size (it can be hidden completely in hand) output light stream is satisfying - it's good enough for the trip to basement or to be used as emergency light in bathroom.
As problem with the switch was getting annoying it was time to dismantle it, which turned out to be pretty straightforward, starting from rubber cap:
Switch itself does not seem to be serviceable, but I washed it for an hour in isopropyl alcohol and then I've poured drop of synthetic oil (popular FINISH LINE green bike chain lubricant) inside - so far this is working.
Another issue (after few years of sporadic use): it seems like "+" cell contact is also not reliable and it might turn off whan shaken. Some cleaning helped, I've also put piece of paper inside to make the cell bounce less, but I'm not sure if this would be permanent solution.
