TCP port scanner, spews SYN packets asynchronously, scanning entire Internet in under 5 minutes.

World's fastest and most advanced password recovery utility

John the Ripper jumbo - advanced offline password cracker, which supports hundreds of hash and cipher types, and runs on many operating systems, CPUs, GPUs, and even some FPGAs

Nmap - the Network Mapper. Github mirror of official SVN repository.

hydra

ZMap is a fast single packet network scanner designed for Internet-wide network surveys.