Most of the hackers would have heard about Backtrack. Weakerthan is another Linux based pentesting distro which is really good.. I think Weakerthan is second best OS for hackers after Backtrack.

Weakth4n Linux is designed primarily for penetration testing. It’s Built from Debian Squeeze.

Tools:

•  BRuWRT-FORSSE v2.0
•  Easy-SSHd
•  Web-Hacking-Portal v2.0
•  Perlwd
•  Netgh0st v3.0
•  YouTube-Thief!
•  Netgh0st v2.2
•  DomainScan
•  ADtrace
•  Admin-Tool
•  Tartarus v0.1
•  and much more….