Thanks for the lists, River Man; I'm checking a lot of those out now (the allmusic links are a great timesaver!). Nice to see a fellow Ochs fan.
Three more relatively obscure artists (stealing your allmusic idea):
Johnny Ace; The greatest 50's singer bar none, and I'd rank him ahead of most people that came afterwards. Despite the cliched title, My Song is about the most moving track I've heard.
allmusic
Townes Van Zandt; The studio albums are, almost without exception, extremely disappointing. The live releases, though, are amazing. Live At The Old Quarter has been immortalized as a classic, but I prefer Rear View Mirror.
allmusic
The Attractions; Maybe I'm just weird, but I rank the Attractions without Costello over all of the records Costello made without the Attractions.
allmusic