NetGuard - NetGuard
AFWall+ - AFWall+ (Android Firewall +) - iptables based firewall for Android
RethinkDNS - 2B+ Android users deserve access to a safer and open Internet.
TrackerControl - TrackerControl allows users to monitor and control the widespread, ongoing, hidden data collection in mobile apps about user behaviour ('tracking').
Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
Blokada - The best ad blocker for Android. Free and open source.