Solite 250 headlamp.
There are smaller headlamps than the 149-gram Solite 250, but their battery life and brightness suffer. The Solite packs 250 lumens, up to five times as much as the average mini headlamp, so you'll rarely need to run it full blast and worry about it losing power when you're navigating a dark ravine. It lasts for 20 hours on low power and 100 hours on read-light mode. [$150; lightandmotion.com]