Interviewers ask this question to find out what sets you apart from the other qualified applicants. Don't quote from what is already written on your resume; find something to tell the interviewer that she/he doesn’t already know about you. Don't fret about proving how you are 'unique'; instead, focus on establishing value.

For e.g. you could say, ‘As my resume states, I have over XX years of experience working in XX field. What isn’t stated there is that I am a goal-setter; once I set myself a target at work, I don't stop until I have achieved it. If you hire me, I anticipate helping your company set and achieve goals that will surpass all of your previous records.’