DNSBL - all.dnsbl.bit.nl
 
This zone contains all IPv4 and IPv6 space by simply including a wildcard for:

*.all.dnsbl.bit.nl. (mapping to 127.0.0.2)
*.ipv6.all.dnsbl.bit.nl. (mapping to 127.0.0.2 and ::2)

It can be used as a fallthrough or catchall list. This list is not open for other entries.