These are my essential apps for my Android device (Nexus7 rooted). All apps are free versions. I'd be interested to know what other peeps consider essential for a happy Android experience.
App ops.
Avast.
Sophos.
KeePassDroid.
SuperSU.
BusyBoxFree.
X-plore.
CleanMaster.
StickMount.
ColorNote.
Kingsoft Office.
Coolreader.
PicsArt.
Dolphin mini browser.
DuckDuckGo.
RetroArch.