Have You rooted your Android Phone and don't know a application most useful for rooted android phone??
I am now posting this article about a application.
Its Xposed Installer:
The Xposed modules like GravityBox, Greenify, Multi Users, APM+ makes your device fast and you can customize your devise as your taste.
Download Xposed Installer:
Visit XDA Developer's Forum to know more about Xposed.