Mountain Ridge
Why? The routing is excellent on what amounts to a mediocre piece of property (most architects wouldn't know how to deal with a hillside like that). The bunkering, restored by Ron Prichard, is fearsome and brilliantly placed. Most of all, the greens are out of this world. These are still the most fearsome greens I've ever putted, and the recovery shots the golfer is asked to hit around them are endless.
Most Ross courses have the great routing, great bunkers, and wild greens, but Mountain Ridge has them to a greater degree.
Of course, with some tree work and continued restoration, Teugega would win this competition going away.
As an aside, Donald Ross's birthday is a good time to note that I've seen Donald Ross's birthplace in Dornoch, Scotland. If that's not a GCA dork landmark, I don't know what is.