Wind up torches
Whenever the power goes off in your home, you end up fumbling for candles or rummaging through drawers only to find that your flashlight's batteries are long gone. The solution is both illuminatingly cheap and inspired.
These torches work simply by winding up the handle (one minute provides around 20 minute's worth of light) to produce a powerful beam. Perfect around the home but also a godsend for in the car as flat tyres have a habit of striking on rainy nights.