I used to use Mag Lites exclusively and still have a 3-D Cell in my pickup. For the past few years though, I've been using the small lithium battery combat lights. I have a Streamlight Scorpion and a Pelican M6. They are cheaper versions of the Surefire lights that have become popular in recent years. The batteries have a 10 year shelf life so you're always guaranteed to have light when you need it. And what a light it is! It's literally blinding, which is why they're used as combat lights. The drawback is that they supposedly only have about an hour of continuous runtime. Having said that, I've had the Scorpion for a few years and have only had to change the batteries once and haven't changed them in the Pelican in the two plus years I've had it. Once you get used to a light this bright it's hard to go back to the Mag lights. It always seemed like the batteries were dead whenever I grabbed a Mag. Also, the lithium lites are a defensive weapon all by themselves. If you're walking along in the dark and someone acts like they may wish to do you harm, just hit them with the light and they are effectively blinded. It's that bright. I'm definitely a convert.