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LED headlamp, one per person
Hands-free light so both hands stay free for stairs, latches, and a child's hand. One per person removes the argument about who gets the flashlight.
Why here. The first minute of the first outage is a dark house with people moving through it. Falls are among the most common injuries of a power outage and among the cheapest to prevent.
“A headlamp is camping gear. A flashlight is fine.”
A flashlight occupies a hand. Everything you will actually do in a dark house, carrying a child to bed, finding the breaker box, opening the cooler without letting the cold out, works better with two hands. Headlamps also cost less than the flashlights most people buy. If you already own good flashlights, you are not behind, but add headlamps before you add a second flashlight.