I never actually got asked that, but when I was planning on it I was going to say something along the lines of:
I would hope you would tell them how great of a fit I am for the school, I am _____, ____ and _____ which will fit in great with your schools goals ____ and ______. Also the such and such programs that you have here would really help me attain my future goals. (the blanks and such and suchs depended on the school) Also, I don't think I mentioned on my applications that I am conversant in Spanish and Sign Language.