As soon as I read the title of this thread, Sound Tradition came into my head. And although Mysha has beaten me to it, I heartily support their nomination.
I suppose if Fisherman's Friends are included, that opens the door to all shanty crews. Three Sheets to the Wind and The Longest Johns are two of my favourites. If a duo qualifies, then Lynne Heraud and Pat Turner are also wonderful.
Garry