Opera Max is one of the apps I really really love, because of it's simple UI and all the great features.
Opera Max is a data-management and data-savings app that shrinks videos and photos on almost any app on mobile data connections, as well as WiFi. Extend your data plan by up to 50% for free.
Although when this 50% will never be reached I think the app has a good right to be here.
In my opinion the app's most advantage is the data management. You can choose which apps are allowed to use your mobile plan / wifi and with the latest update also which apps are allowed to use internet in the background.
You also have a great overview about which app used how much data and how much you saved with Opera Max.
The app is very helpful if you have a small data plan and use much video / music streaming or social networking with apps like Instagram.