Flashlight apps are a dime a dozen on the App Store, but Light, an app by developer, and Apple blogger, Erica Sadun was different. It bent the rules by adjusting the brightness of the display, something that wasn't (and still isn't) allowed in Apple's API.
But in the case of this app it was hugely helpful. Say, for instance, you had your brightness turned all the way down. When you launched Light it would bump it all the way up, then return it back to that same level as soon as you quit the app. With other flashlight apps on the App Store you're required to first dig through your iPod or iPhone's settings to tweak the phone's brightness, making them pretty much useless.
Light lives on, although Sadun only offers it as a free app to fellow developers, and not in the App Store.