What about these TH3Cs' and "SnowLEDs" I've heard about?
I use the THC3's direct drive in Mini Mags. They're great with lithiums, OK with fresh alkalines, and not very bright with NiMH's. Still, I use them with all three types of batteries. I'd say with lithium's, the THC3's are quite a bit brighter (overall) than a stock Mini Mag incan, about the same with alkalines (after the initial sag) and dimmer with NiMH's. But, for specific purposes, all three chemistries work well, and the runtimes are out of sight! I estimate 50 hours with lithium's and who knows with alk's and Nimh's.
I think the Peak snows are whiter, but the THC3's aren't bad, with just a hint of blue. Way better than Nichia's. I don't know where you can get the "snow's" anymore though.
Dave