Hmmm. Going to be used routinely right?
Seems like you'd want to avoid pricey batteries like the Lithium 123a.
As far as rechargeables goes...this is a great idea. Although, unless your flashlight has a removeable battery module, you could be "out in the cold (dark)" when the battery suddenly quits on you (rechargeables run pretty flat, then suddently dive off to nothing). So...I'd recommend a light that uses commonly available battery sizes like the AA. You can use NiMH rechargeables and always have a spare set handy. Heck, you can even get lithium AAs for cold weather emergency use or just regular Alkalines for back up.
Now, if we are talking bright spot type lights that run off of NiMH AAs...I'd recommend the UK 4AA AS2. It is quite pocketable (probably the best 4 AA light for that) and has a really easy to use switch for one handed use. It will light up a house number from probably 100-150 feet plus a piece of the surrounding house as you look for the numbers.
Others to consider...
PT Surge, REALLY bright but not a spot type light (depends on how hard it is to spot the numbers in the first place). Runs on either 4 or 8 AAs; nice switch for one handed operation.
Stealthlite, smallest, tightest (and therefore brightest) spot in a 4AA light; also has a nice switch for one handed operation.
If your light is never going to leave the truck...then something you can run off of the cigarette lighter is probably best. Something like that can be hugely bright!
If you truly want the "smallest, brightest" light, you're probably talkin' the PT Rage (4 AAAs). Although, it has a broad beam and requires two hands to turn on. But...it is really small and really bright.