I understand that you may not be best suited to the weakness question (article coming soon on how to address those types of questions). However, in the interim, you should be well aware of some benefits which you are able to offer an organization. What has your boss said about you that was positive? What did you contribute to a company? Did you increase revenue? Decrease costs? Improve customer satisfaction? What benefit will a future company receive from your work ethic, knowledge, skills, and personality?
Know a contribution that you made to a company. Share examples that make you who you are. Have a one minute sales pitch about yourself that will speak to your effectiveness and ability to go above and beyond the job for which you are interviewing.