Well, almost any language can be used to exploit vulnerabilities. I think some of the most common languages are going to be Python, Ruby, Java/Script, and anything of the C breed. For local/program exploits, I would recommend you to get familiar with assembly code, as most things will get broken down to assembly before machine code.
I don't care how ‘secure’ your systems are. If you have stupid people running them and using them, you can't win.
For those that know