Slughaus “Bullet 02” Mini LED Keychain Flashlight
I've seen some keychain flashlights in my day, but the Slughaus Bullet 02 (which got its start as a Kickstarter project several years ago) has got to be the tinyest one I've ever seen. The thing measures only an inch long and weighs a mere 5 grams!
The 20 lumens of light it puts out wouldn't be the most impressive measure in the world for most flashlights, but at this size it's definitely not a bad thing to have around when you need it.
They also designed the Bullet 02 to be waterproof, fireproof, and shatterproof so you never have to worry about it getting destroyed, whether you keep it on your keychain or attached to the outside of a bag.
Get the Bullet 02 for $19 on Amazon. Comes with three LR41 button cell batteries to get you started.