A maglight is nice because (as mentioned) it can be used as a baton, but in general, I'd suggest a Surefire, and depending on your price range...
$30 G2
$50 6P
$80-100+ E2E, L4, and so on.

Now, if you really don't want to pay these prices for a flashlight, a Brinkmann Maxfire offers essentially the same powerful, focus free beam as the G2, 6P, and E2E for $19.99. It's not as ruggid, but still one of the best buys for the dollar; these can be found online, at walmart (if there's one where you live), etc.

Now, from the serious to the ridiculous...
If you want the biggest, baddest light out there, you can shell out $2,900 for a 2,000 lumen (!) Surefire Beast.
It's fun to make jokes about this thing.... the first flashlight with recoil, the first crew served flashlight, the first flashlight you start with a pullchain, the first flashlight requiring a rifle sling, man portable 747 landing light, etc etc etc <img src="/images/graemlins/grin.gif" alt="" />

Bad boy uses 20 CR123's.



Nope, girl doesn't come with it, even at that price! But I'm sure you can impress them with the size of your flashlight <img src="/images/graemlins/grin.gif" alt="" />