I use a Surefire L1. It has a variable output from 10 lumens to 65 lumens and is small enough to fit in with all the other junk I carry day to day. It has the same output as the 6p series lights, but with only one battery. The low power feature is handy for finding keys in the dark, checking on the baby, and such. The 65 lumen output is nice to have on hand for SD use or when more is needed. It's just long enough and shaped right that you could hit with it if you had to, without being the obvious weapon like they make in other versions. I bought two L1s, a stack of spare batteries, battery carriers, and was under $250. It was a lot cheaper locally than on Ebay or anything I found.
L1 LumaMax® LED Flashlight in Bright Blue, Green, Red or White from SureFire