I've got the black diamond ion which is 22 lumens bright with a low setting that is probably 6 or 8. I think it burns for 25 hours on low, and that's usually what I take on most trips because it only weighs 28 grams – so it's only slightly heavier than the human soul. I keep a tiny photon style light (princeton I think) on a lanyard with my SAK and whistle as a back up.
One of my favorite lights for – that's borderline overkill but light and high quality I think – is the Princeton Tec Remix. It's around 2.5 ounces, 100 lumens, and has a a single bright LED and three smaller LEDs. I like that it's all black band, lamp and all and it does not involve all the goofy colors that so many headlamps seem to use these days.
Lastly – there are so many GREAT little EDC lights to borrow a preppers term. I have a single AA Fenix (LD01 I think) and a AAA LD05. I also have a single AA oLight. All of these are pretty amazing and have great burn times for the light they put out. the oLight is downright dangerous; it could be used as a weapon. But, these little guys can clip on a belt, belt loop or hat bill. In the future I may resort to carrying only one of these and ditch headlamps altogether, but the BD ion works great, and as little as I use a light, is all I need for now.
Another user here posted about the Klarus Mi6, and I want one. It looks like a lot of light in a small package – kind of like the Zebralight headlamp, but I think it's over 100 lumens. As Bob G. and others noted, it really depends on what you're doing and when/where you're going. For the money – if you just need to find stuff in the dark, go with the ion, or even a photon freedom with the hat clip.
One note, I like to make sure if I'm bringing a GPS, or any other electronics, that I can match batteries for all such items and not have to carry a variety of spares, but if the light – like my Remix – requires more than one battery, this effort becomes pretty moot.