Essay over Spring Break - Duality ideas

My teacher assigned an essay on the topic of our choice that's due the monday after we get back from Spring Break. Anyway, I was thinking on writing on the subject of duality. I could talk for pages on Raskolnikov and his name meaning 'schism' as well as his schismed nature and yadda yadda yadda. However, I can't write an analytical paper on one character. If anyone has any other characters, themes, motifs, symbols, etc. that embody some sort of duality please PLEASE let me know! Thanks all!