For EDC aspects of this issue, I have my Fenix EO-1 and DR Photon on my keychain as "last best friend" back-ups. In my "walking around" EDC kits for briefcase or day bag, I have a Princeton-Tec Scout headlamp with extra batteries, an incredibly small, lightweight and practical multi-night unit. I also have recently added a Zebralight, 1 AA, SC-51E flashlight with opional headband. Expensive, but very long lived for a light with such a high maximum brightness. There's also another Phton in the bag(s).