nUbuntu is a Linux distribution based on the popular distribution Ubuntu, tailor made for security testing.
nUbuntu is a project to take the existing Ubuntu distribution and remaster it as a LiveCD and Desktop distribution with tools needed for penetration testing of servers and networks. The main idea is to keep Ubuntu’s ease of use and mix it with popular penetration testing tools. Besides usage for network and server testing, nUbuntu will be made to be a desktop distribution for advanced Linux users.

Small in size compare to Protech OS or BT also have some demerits as it is still in Alpha stage. Lets hope for the best in future releases.
Screenshots: Security Distro
Download: nUbuntu