Favorite single String Quartet movement?

If you have to choose just one movement that is your favorite string quartet movement ever, which would it be?

For me it is definitely the pizzicato-laced 2nd movement of Ravels String Quartet in F:

Apparently this quartet got a very bad reception the first time it was performed and Faure - who it was dedicated to - hated it.

Anyway - what's your favorite of all time?

It may be a cliched answer, but I guess I'd say the slow movement from Beethoven's A minor quartet, Op. 132:

Notturno, from the String Quartet no. 2 by Alexander Borodin.

There are others I rank highly, like the 2nd movement of Tchaikovsky's String Quartet no. 1, or the opening movement of Hugo Wolf's String Quartet, or even the second movement of Rachmaninoff's String Quartet no. 2 (and of course, the classical quartets by Haydn, Mozart, Beethoven, and Schubert), but if I'm being honest, it has to be Borodin's Notturno. The perfect balance between melodic beauty and proportion is unparalleled, not to mention being one of the most moving pieces ever written (at least in my opinion).