When it comes to duets, in my book, it is difficult to match the exquisite beauty of the Flower Duet from Lakme. I have several versions on CD, starting with the opera starring Mady Mesple. Well, here are some other attractive duets.
Dmitri Hvorostovsky and Aida Garifullina performing "Moskauer Nachte" on 22 June 2017, two months before the end. Yes, the microphone is clipping a little in places. Yet Dmitri's emotion is enough to bring a lump to the throat.
Here are Anna Netrebko and Rolando Villazon in 2006 singing "Caro elisir! sei mio! ..." from Donizetti's L'Elisir d'Amore. The chemistry is apparent.
Justyna Steczkowska i Pawel Delag singing "Mala moja, malenka" from the only arthouse CD Justyna released (unless you count her couple of lullabies CDs). Alas, some of the few songs from the CD on YT seem to be truncated to half their length on the CD.
V Shivapriya and B R Somashekar Jois dueting in the Konnakkol "percussive/rhythmic scat" genre.
Lila Downs and Juanes performing La Patria Madrina. This is a reason for high-power HPAs.
JJsays (Jillian) and her mom Nancy perform "The Moon Represents My Heart"
Sophia Loren and Paolo Bacilieri perform "Tu vuo fa L'Americano" in the movie "It Started In Naples". YT clip posted by Rosanna Molignini Brockstedt. The same poster has also posted a hilarious clip from the movie "Pane Amore e..." of Sophia Loren and Vittorio de Sica dancing to the tune of "Mambo Italiano". If only a good duet version of the song were posted with the same clip as visual, it would be a showstopper for me.
I think the below is the album (LP) version of the preceding movie song.