People having conversations around me are my biggest productivity killer. Sadly I'm in a small open office environment where it is culturally acceptable to have personal conversations with your coworkers at any time of the day, as if we were in a break room. Our manager is one of the worst offenders. None of my colleagues are developers so they're not really bothered by it as much, but I have a very hard time being productive and writing good code when I can't hear my own thoughts. It's very frustrating.