You may interpret “lesser-known” however you like. As a guideline, though, think about that local radio station that plays Christmas music all season, and then think of something you probably won’t hear there.
It can be an original song. It can be a version of something traditional. It can be anything, really - just looking for something I don’t hear a thousand times every December.
I’ll start with Art Carney’s weird and wonderful beatnik-rap rendition of “‘Twas The Night Before Christmas” from 1954:
(There may be some overlap here from @Saint_Cad’s Spotify list thread; that’s OK. But I think this is a different enough idea to have its own thread.)
A good deal of my musical taste was formed by Christmas in High Fidelity by George Melachrino. This particular track was recorded at Abbey Road Studios in 1955, with the aid of a telephone line running to a nearby church. (They didn’t have multitrack then, so it had to be mixed live.) Hark! The Herald Angels Sing - YouTube Listen to it loud.
My all time favorite Christmas song is Merry Christmas Baby by Charles Brown, but I don’t think is qualifies as lesser-known. So here’s Denise LaSalle: Santa Claus Got The Blues - YouTube
I don’t know how “lesser known” it is, as it was (and still is) fairly popular in my circle of friends, but the 1997 album “Merry Axemas” has always been a holiday favorite of mine.
The full album is on YouTube, maybe iTunes (I can’t check just this moment), and the CD is, obviously, available on Amazon.