Documentation and Support
You've built a really cool mobile app for iOS and/or Android.
Now you want to be able to launch it from a webpage or email. Not only that, you want to load it up to a specific section of the app -- say, viewing a certain article in a news app, seeing a particular image in an social-network app, or entering a particular chatroom in a chat app. Not only that, but maybe you have a web-based version of the same app. You want one link to be able to intelligently launch the app (if installed), download the app (if not yet installed), or show the web-based version (if on a desktop, unsupported platform, or if the hoser simply doesn't want to install your masterpiece yet).
You want Deeplink!