I love it when the tuba gets the melody. Rózsa's elephant music in The Jungle Book got me into film music. Actually, the melody dropping into the bass is something I adore in general ... much of Ronald Stein's The Haunted Palace was composed in this vein.
I love it when the full symphonic ensemble suddenly recedes, leaving only one section, such as brass or strings.
I love the accordion schmear Shirley Walker invented for Willard.
Speaking of Shirley, she was a master of orchestration. I've just been reviewing LLL's Batman set for FSM, and I'm constantly struck by the neat things she's doing. She's completely unafraid to let the melody take a back seat to whatever interesting things are going on in the harmony or countermelody. I'm listening to "Crashing The Party" from the episode "Joker's Favor" right now ... she's got the woodwinds stratified across the orchestral ranges, she's letting these heady accompaniment figures break into the foreground ... it's interesting and capricious and fun. One thing she's doing right now that I love is when two distinct instruments in different ranges have lines that intertwine, sometimes doubling, sometimes diverging -- in this case, french horn and clarinet, while the melody whickers away in muted trumpets.
With Angela Morley's passing, I've also been doing a lot of listening to Watership Down. God, that's a wonderful score. And she was a beautiful orchestrator as well. She knew how to use a whole section to good effect, particularly strings, but she also knew how to arrange things so that a solo instrument could really shine through and have an impact.