John The Ripper
John the Ripper is a free password cracking software tool. Originally developed for the Unix operating system, it can run on fifteen different platform.
NCrack
Crack is a Unix password cracking program designed to allow system administrators to locate users who may have weak passwords vulnerable to a dictionary attack. Crack was the first standalone password cracker for Unix systems and the first to introduce programmable dictionary generation.
Hydra
Hydra is a parallelized password cracker which supports numerous protocols to attack. It is very fast and flexible, and new modules are easy to add. This tool makes it possible for researchers and security consultants to show how easy it would be to gain unauthorized access to a system remotely.
Medusa
Medusa is a speedy, massively parallel, modular, login brute-forcer for network services created by the geeks at http://Foofus.net. It currently has modules for the following services: CVS, FTP, HTTP, IMAP, MS-SQL, MySQL, NCP (NetWare), PcAnywhere, POP3, PostgreSQL, rexec, rlogin, rsh, SMB, SMTP (VRFY), SNMP, SSHv2, SVN, Telnet, VmAuthd, VNC, and a generic wrapper module.
Aircrack-ng
Aircrack-ng is a Free and a Very Common Tool Used for Cracking Password of WPA,WPA2 Hashesh. It is Mainly Used For Wireless Pen Testing. By Using Aircrack-ng You Can Crack Passwords Via Brute Force or Wordlist Based Attack.