DNS66 allows blocking host names via DNS. This can be used for ad blocking. It also allows other DNS servers to be added, for more privacy.
Compared to AdBlock Plus, this works without proxy stuff; and it also does not require root, like AdAway does: DNS66 establishes a VPN interface, and redirects DNS server traffic to it. The VPN interface filters the traffic, only allowing queries for hosts that are not blacklisted.
A host (list) can be configured as allow, deny, or ignore. A later entry in the list overrides a previous entry.
Custom DNS Servers can be configured as well, using the same UI, but no differentiation is made between ignored and denied servers.