Dropbox - iOS app automatically pauses Camera Upload when the battery is running low.
British Gas - iPhone app has a button to turn on the camera light when submitting a meter reading.
/via Jaik Dean
Foursquare iOS app - if you drag your uploaded photo to the left, you see a hidden mascot holding a camera.
Facebook Camera - After clicking the install now button, a pop-up message offers to text you a direct link to the app, with your phone number pre-filled in.
/via Taylor McKnight
iOS - If you tap the camera icon in the lock screen of iOS 5.1, it bounces up to encourage you to slide.
Batch - When enabling the camera flash, the camera icon on the shutter button gets a little white flash.