As a work light - my Pelican 2xAAA mity-light is diveproof (did many years of 120ft dives) and has worked at 15,000ft. It claims explosion proof - not tested it but I haven't exploded yet!
It's a regular bulb not a LED but one I've had for more than 15years is still going strong.

As a EDC I have a bunch of cheap LED coin cell LEDS secreted in most pockets and on most keyrings.
And in the winter I have a couple of single AAA Fenix knock-offs.