What song should I sing?

I am trying to find a good song for my high school talent show. I need a song that shows off my vocal range and my strong voice. I would prefer a song that has piano accompaniment that I can play while singing. I've already performed Love Song by Sara Bareilles, And So It Goes by Billy Joel, A Thousand Miles by Vanessa Carlton, and Samson by Regina Spektor. I would like a song that is not very well known, but has a powerful meaning or message. :)