13. "Stay" (feat. Mikky Ekko) (2012)
By the time Rihanna released Unapologetic, ballads were hardly new territory for her. But something about her piano-driven display of utter vulnerability on "Stay" makes the song one of her most emotionally provocative performances to date. Newcomer Mikky Ekko served as the singer's perfectly matched duet partner as they detail the two sides of a pair fighting to keep a relationship together. Co-written by Justin Parker, who was behind the similarly emotional balladry of Lana Del Rey's early tracks like "Video Games" and "Ride," the track finds success in its simplicity, setting the stage for her stripped-down follow-up album, Anti.