I'm not a big fan of the Greenville Jackson as it looks like it was cut out of a newspaper; also I can't rank a RPPC as a top one as they're just too varied and don't have the history of a regular postcard. That being said I WISH there was such a thing as a Wagner-type PC, especially since I own two of the ones on the list.
As someone who owns many rare Cobb PCs, I think my favorite two (which encompasses looks and rarity) are the Rose PC and this one:
