When used under full power, the MagLite Mag-Tac LED light can put out 543 lumens, which is more than a 40-watt incandescent bulb, and can be used for up to two and a half hours straight.
Then when the battery dies, you can just plug it right into your car's cigarette lighter outlet and let it charge right back up.
If flashlights that use disposable batteries are too old-fashioned for you, this one should do the trick perfectly.