Some Pen-Test tools, almost all can find in BackTrack3
./snmpcheck-1.6.pl -t ip
./nikto -h ip -p 80
openssl s_client -connect 18.104.22.168:443 | more
nmap (for OS detection, it needs at least 1 open and 1 closed)
unicorn scan (for OS detection, just need 1 open or 1 closed)
More to learn..