First of all, pretty wild to see Isham, Jones and Poledouris on your list, GerateWohl — great composers with a variety of scores on their resume.
This question can be answered in a number of ways — there are composers where I only have one score, because I’m not familiar with the rest of their work. Or I AM familiar with their work, but have only landed on one to own. Or they’ve just done one, or close to one. Etc.
So taking ALL of that into consideration, I would need to list literally HUNDREDS of “one-off” titles in my collection. But I’m going to limit myself to famous or semi-famous composers with pretty extensive catalogues (in film music and/or non-film music), and choose 10 from them. So maybe something like:
Air – THE VIRGIN SUICIDES
Carter Burwell – ROB ROY (well, plus the WSA compilation)
Goblin – SUSPIRIA (plus a compilation)
Jerome Moross – THE BIG COUNTRY
Michael Land – THE DIG
Paul van Dyk – ZURDO
Sergei Prokofiev – ALEXANDER NEVSKY
Simon Franglen – AVATAR: THE WAY OF WATER
Toto – DUNE
Tom Tykwer & co. – PERFUME: THE STORY OF A MURDERER