Shell Detect is the FREE tool to detect presence of Shell Code within a file or network stream. You can either provide raw binary file (generated from Metasploit) or network stream file as input to this tool.
These days attackers distribute malicious files which contains hidden exploit shell code. This can hijack your system if the shell code gets executed directly. In such cases ShellDetect may help you to identify presence of shell code (as long as it is in raw format) and help you to keep your system safe.
New version 1.1 provides support for detecting Unicode Shellcode. Now you can directly feed unicode shellcode without converting it to binary or raw form. For example, %u4141%u4242 can be detected directly from the input file.
ShellDetect one of the nice tool written by Amit Malik, you can see all his work here.
For more interesting details, kindly visit Shell Detect