NOW, they are advertising the latest LED monster light, the M6LT Guardian, as 900-Lumens, and uses SIX 123A batteries in a quick-change magazine, even though the flashlight's listed run time is an impressive 3.25 hours! The only problem I can see is there are no lower-power settings, unlike their previous 400-Lumens model, which has a 70-Lumens brightness setting. Surefire also sells a spare 6-battery carrier, spare battery magazine, and red & blue lenses for the 2.5-inch bezel lens lights.
Check it out - that's a LOT of light in a damned small package (and you're gonna' pay for it):

It looks like a GREAT light, but the price is also quite steep: $425.00
Flashlight description:
Specifications
Max Output -- White Light 900.0 lumens
Tactical Runtime* 3.2 hours
Length 8.20 inches
Bezel Diameter 2.50 inches
Weight w/Batteries 17.1 ounces
Batteries 6 123A (included)
*Runtime (at highest setting for multiple-output flashlights) until output drops below 50 lumens
Description
M6LT
The M6LT Guardian—a powerful LED upgrade of our incandescent M6 model—is a long-running extended-range flashlight featuring a tight 900-lumen beam focused by a 2.5-inch Turbohead TIR lens. The brilliant white beam can dominate potential aggressors by overwhelming their dark-adapted vision, or it can reach far into the night as an amazingly effective spotlight/searchlight that fits in a coat pocket. The M6LT's high-strength aerospace aluminum body has deep machined grooves to provide a secure hold with cold, wet, or gloved hands, and is finished with Mil-Spec hard anodizing for excellent corrosion and abrasion resistance. The tactical pushbutton tailcap switch provides secure, ergonomic activation control: press for momentary-on, twist for constant-on. The M6LT is powered by six high-energy 123A batteries held in an easy-load battery magazine.
[NSN: 6230-01-529-6196]
Features
Virtually indestructible LED emitter regulated to maximize output and runtime
Large Turbohead TIR lens produces tight, extended reach beam
Coated, tempered window resists impact and thermal shock, maximizes light transmission
Deep machined grooves in body provide secure hold in all conditions
High-strength aerospace aluminum body, Mil-Spec hard anodized for extreme durability
Tactical tailcap switch—press for momentary-on, twist for constant-on
Tailcap switch locks out to prevent activation during transport or storage
Weatherproof O-ring and gasket sealing
Includes high-energy 123A batteries with 10-year shelf life