Request for arp-scan tool
Could you please add arp-scan to BT4? This is an ARP scanning and fingerprinting tool. I'm not allowed to post links yet, but a google for "arp-scan" should find it.
It is available as a source tarball. There are also binary packages for Debian, Ubuntu, Fedora, RHEL, FreeBSD, OpenBSD and probably others.
I find this invaluable for quickly identifying live hosts on the local LAN, detecting hosts that don't offer network services like firewalls, and fingerprinting systems that can't easily be fingerprinted in other ways.