Busybox (Root Required)
This application is an BusyBox installer for Android.
Flud
Flud is a simple and beautiful BitTorrent client. It is better that utorrent and any other torrent clients available on play store.
Gallery Doctor
It identifies similar, duplicate and bad quality photos and gives you an option to remove them. It is very helpful to remove unwanted whatsapp photos.
Greenify
It forcefully kills apps like facebook and whatsapp that runs in the background, consuming battery and internet bandwidth, push annoying notification.
Loader Droid download manager
LoaderDroid is a Download Manager. The best feature of this app is resume capability. Even if the link breaks we can resume downloading after providing alternate link of same file.
MK Explorer
MK Explorer is a simple, fast, beautiful and ad-free file manager.
Office Lens
Office Lens trims, enhances, and makes pictures of white boards and documents (and even photos) readable.
Pulsar Music Player
Pulsar is an adfree music player. It can display songs by folders also.
Via Browser
It is the fastest, the lightest and the most beautiful browser. Chrome and Firefox are nothing compared to this browser in terms of speed.
Vlc
One of the best video players in android. It is ad free, can play any type of videos and can download subtitles also. The only disadvantage of this app compared to mx player is that it displays all directories even empty directories.
Zero Dialer
ZERO Dialer & Contacts is the smallest, fastest, simplest and ad-free dialer. It supports fast dialer with T9, quick search for contacts, block spam calls, rich themes, and dual SIM.
Zero Sms
This is the only app in playstore which supports dual sim and can also display instant message.
Not in Playstore :
AdAway (Root Required)
AdAway is an open source ad blocker for Android using the hosts file.
Blokada
The best ad blocker for Android: free and open source. It creates a vpn connection to block ads. Therefore it doesnot need root.
Blackmart Alpha
Blackmart Alpha is a market alternative to the Google Play Store where you can download paid apps for free.
Lucky Patcher (Root Required)
Crack paid apps and remove ads from apps.
Tubemate
Download videos from websites like youtube and facebook.
Others :
ZArchiver
ZArchiver is a program for archive management. It is free and ad-free.