Not my favorite wines, but I liked very much Bodega Trapiche. They re-purposed an older winery and rail-shipping warehouse as a visitor center. And to be fair, the wines you can taste there are harder to find (and better) than the Trapiches you get elsewhere.
In a very different vein, Domaine St Diego: excellent wines, small "garagiste" style winery. I visited a few years ago and I had the enourmous luck to meet Mr. Mendoza, the head enologist. I bought several of their bottled offerings, but I heard you can bring your own "damajuana" to be filled with their younger malbecs...tempting...
Salud!