A few orchestral ones:
Strauss Don Quixote - the solo viola tunes the C string down to B for a
passage in the middle of the piece. The same composer has all the second
violins tune the G to F# at one point in the 'critics' passage in
Heldenleben.

In the first version of Stravinsky's Firebird the famous harmonic glissando
was on the violins' E string tuned down to D. In the later version he
used the D string, sacrificing the higher octave in the interests of
practicality.

Paul Silverthorne