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.
1. No system is safe.
2. Aim for the the impossible.
3. Have fun in cyberspace and meatspace.