In classical music, it's occasionally seen in Baroque music, and Paganini used it some, but rare otherwise.

Post-Baroque examples I know of:

* Mozart, Sinfonia Concertante for Violin and Viola: the piece is written in E-flat major, and Mozart apparently intended for the viola soloist to tune up a half step and play as if in D major. Most violists prefer to play in standard tuning, in part because the string tension gets too high in scordatura with the modern A.

* Schumann, Piano Quartet: the cellist has to quietly tune the C string down to B-flat for the end of the third movement, then tune back up to C for the fourth movement.

* Saint-Saens, Danse Macabre: the solo violin's E string is tuned down to E-flat to create a tritone on open strings.

* Richard Strauss, Don Quixote: there is a principal viola solo passage where the principal violist tunes the C string down to B for that passage, and then tunes back up to C in the next long rest. Often the principal violist has a second viola already tuned and set aside for that passage, and switches during the rests. When my semipro orchestra played it, our principal violist didn't use a second viola, but installed a fine tuner on her C string just for that one concert.

* Richard Strauss, Ein Heldenleben: the second violins have to tune their G strings down to F-sharp for a passage.

* Stravinsky, The Firebird: the first violins are instructed to tune their E strings down to D for the introduction, in order to play a series of natural harmonics. Typically this is ignored and the violinists play the harmonics an octave lower on the D string, with much the same effect.

* Stravinsky, The Rite of Spring: at the end, the cellos tune their A strings down to G-sharp in order to play a quadruple stop using that open string.

Most of these tunings are used either to play a note below the instrument's normal range, or to play chords that would be difficult or impossible without scordatura.