Bennie & The Jets - Elton John arranged for String Quartet
Bennie and the Jets for string quartet. Only took me five years to finish this one.
The lines between good arranging and composing are pretty blurry IMO, which I don't think I'd learnt when I started it.
(Ignore the weird misplaced bowings - Sibelius seems to either be able to do good parts, or good score, but not both.)