7. Barbra Streisand With Blake Shelton
From Streisand's duets album Partners
While the sweetly sentimental acoustic duet "I'd Want It to Be You" is more in Babs' adult contemporary wheelhouse than Shelton's bro-country territory, The Voice mentor meshes nicely with the Oscar winner on a heartwarming ode to lifetime friendship. That the song winkingly nods to his hit "Honey Bee" and her Funny Girl past is just the earnest icing on this cross-genre cake. Although the pair didn't record in the studio together — she cheered him on by phone — Shelton can claim a bit of Streisand history as Partners' debut atop the Billboard album chart made the stage-and-screen star the first artist to score Number One albums in each of the last six decades. He also no doubt got a kick out of The Tonight Show host Jimmy Fallon's "impersonation" during Streisand's appearance on the show.