What are some good songs for a duet?

Question

My friend and I are thinking about doing a duet for the annual concert at school. She wants to play guitar, and she wants me to play the piano. Two songs came to my head: Runaway Train by Soul Asylum and Red Rubber Ball by Paul Simon. Give me some more suggestions and/or tell me what you think of these.

Answer 1

Take me home country Roads!

Answer 2

How about Layla by Eric Clapton?

Answer 3

No air by Jordan sparks and chris brown...or maybe something more classical...and disney like...beauty and the beast...or a whole new world...