I don't know if the following qualify as unique, but a couple of very much overlooked labels with great sound are the Artist House LP's and the pressings from A&M records Horizon's division, representing abstract Jazz (post bop?) artists of the 1970's.
As it turns out, both of these were started by John Snyder and both share wonderful sound with forward looking, creative music by very talented Jazz musicians.
Good examples on the Artist House label are Ornette Coleman, AH-6 (Artist House 6), Andrew Hill, AH-9 and Waymon Reed, AH9410.
On A&M Horizon are Brubeck and Desmond, A&M Horizon SP-703 and two by Charlie Haden, titled "The Golden Number," and "Closeness." These last two are better than many "audiophile" recordings for sound and the music is
Incredible. Literally two of my favorite Jazz LP's.
Lets hear from others here at Audiogon about your rare or obscure titles. It's nice to have a topic dedicated to vinyl and music :^).