Antonín Dvořák's Cello Concerto, op.104 is a favorite among cellists, audiences, and flute players. It features the flute prominently in many solos and dialogues with the soloist.
At the end of the first movement, in the first flute part, Dvořák writes a high B to high C# trill (B3C#4). Most flutists, including myself, tend to forget how to play that trill since it's seldom used in the flute repertoire.