Python is very commonly used for security tools and scripts, but my personal favorite is Ruby. Ruby has a very elegant syntax, has methods that are easy to use, and is easily compiled. It's also the language used in the Metasploit Framework, which is one of the most popular security tools in the world. You can read about the Metasploit team's reasoning for using Ruby here: https://github.com/rapid7/metasploit-framework/wiki/Why-Ruby%3F