The Seventh is usually held in low regard by Mahler freaks, but I’m going to throw it into the ring for the third movement: the supremely shuddery and nightmarish scherzo. I’m also fond of the two “Song of the Night” movements that surround it.
Other favorite Mahler movements, just off the top of my head: the third movement scherzo from the Second, which uses the melody from Gustav’s own song about St. Anthony of Padua’s sermon to the fishes…another fascinating piece of virtuoso orchestration. And the second movement landler of the Ninth – the “dance of death.”