Answers to Avoid
This is not the time to be humble. While you do not want to exaggerate your strengths, you should be comfortable articulating what makes you an ideal candidate. Creating a list of your strengths (as they relate to the job) will help you answer this question with confidence.
On the other hand, you do not want to answer this question with a laundry list of vague strengths. Stay focused on a couple key strengths that relate directly to the position and the company. A focused, relevant answer with one or two examples will impress your interviewer.