A friend of mine once took a hard wack in the face with a big maglite, may have been a 4D... anyway, he reports it was VERY effective. Not sure if the maglite worked afterwards...

...for a 2-AA LED flashlight, I have a Mini-Maglite 2-AA LED, widely available & 1/3 the cost of Fenix LD20.
Maglite has SOS strobe mode, dunno if Fenix does.
Fenix has the turbo/hi/med/lo settings, Minimag has only 2.

Still looking for a reasonably priced single AA or single AAA LED light to replace the single AAA minimag on the keychain.