A discussion on another website asked what people thought were under-appreciation and/or up-and-coming varieties that deserved more attention. The original poster suggested four varieties: Viognier, Cabernet Franc, Tannat, and Bonarda (as it's called in Argentina; aka Charbono in California, or Douce Noire in France and most of the world).
I'm wondering what people here think -- of these four varieties, or others that you think are under-appreciated, or that you've seen a surge of interest in to the point where they might be considered as "up-and-coming" . . . .