I will always have a soft spot for Snurdy McGurdy and her Dancin' Shoes (Nessa).
My first exposure to his Mr. Mitchell's music, and at the time, I had never heard anything quite like it. It took me awhile to "get" it... but to this day, "Sing Song" gives me chills. The slow yet relentless building that finally releases at 6:24 is one of my all-time favorite musical moments.
Great idea for a thread, looking forward to more responses.
Edited to add: the alternate take of "Ornette" on Sound is also a favorite. The cello.... YES!!!