Day 2 - A Flashlight so you can see what you're doing
I mentioned in a recent post a moment when the power went out at a conference I was attending in Las Vegas. Temporary power was restored in minutes (maybe seconds... Time goes slower in pitch darkness.) and we were evacuated from the building immediately. That incident instilled in me the importance of carrying a light source with me. I love this teeny-tiny flashlight because it's lightweight and I can easily carry an extra battery with me.
In that dark moment in the Las Vegas convention center, everyone flipped on their phones. But if we had been forced to depend on cell phones for extended lighting, we would have been compromising the battery life of our primary form of communication and source of information. Keeping a tiny flashlight in your purse, pocket, briefcase, backpack or keychain will certainly be invaluable many other times and not just in an emergency.
Remember that batteries stored in a flashlight lose charge even if they are not used. Remember to switch out these batteries frequently (or carry an extra set), so they'll be ready when you need them.