Root Explorer is a file explorer application for Android that costs $3.99.
Titanium Backup is the most powerful backup tool on Android, and then some. Premium for $5.99
Adblock Plus is a free and opensource ad blocker for Android. It does not require ROOT on Android 3 or higher though it is the best way to block advertisements as ROOT allows it...
Greenify (Donation Package)
Greenify (Donation Package) is the paid version of the Greenify app, it costs $2.99 and has zero in app purchases.