Fenix's E05 flashlight — $19.95
Many iPhone owners rely on their their flashlight apps when they want some illumination on a task. However, modern LED flashlights are able to put out a lot more light and even better, save your phone batteries for more-productive applications. And what if you need to be talking on the phone and looking around in a dark space? I find that the flashlight format is easier to hold onto when searching for that screw that somehow slipped out of your fingers, or when checking out the back panel of a CPU enclosure in the dark underneath a desk.
I have had a Fenix E05 on my keychain for years. It's just a bit longer than a AAA battery and is very lightweight. It puts out a solid light, not super-bright but more than sufficient.
However, I recently decided to upgrade to the Fenix LD15, a more powerful light with a AA battery. It's a bit bigger and thicker (and heavier), but can crank out 117 lumens, which will let you easily see colors across a dark room.