I am sure I have chimed on this thread already. I usually carry a LED Maglite, and either my Black Diamond Storm (totally waterproof headlamp) or a Petzel e+lite.

Earlier this year I picked up a Tactical ballcap from a company called GORUCK. Best ball cap I have ever worn. One reason is under the brim is a soft liner for placing velcro patches and such. I stuck a velcro disk on a photon microlight and stuck it under the brim. Never even remember its there. But I can just reach up, press the button or flick the switch and 'let there be light'