SubBrute
A DNS meta-query spider that enumerates DNS records, and subdomains.
SubBrute is a community driven project with the goal of creating the fastest, and most accurate subdomain enumeration tool. Some of the magic behind SubBrute is that it uses open resolvers as a kind of proxy to circumvent DNS rate-limiting. This design also provides a layer of anonymity, as SubBrute does not send traffic directly to the target's name servers.