Lighting

There is no excuse for not being prepared for the most basic scenarios.
Too many people take the national grid for granted, adverse weather, spikes in demand and vandalism to main stations can all cause the power to drop, and every prepper should be ready for the moment when it does.
Don't forget the basics! Know where your equipment is, keep it in good order and keep spares. It's not rocket science, but it's amazing how many people couldn't find a torch in less than 3 minutes when the time came.