Tom of Seventh Street Cottage asked this question on Garden Web. He named Camellias, Azaleas and Roses; Tea Olive, Althea and Okra as Quintessential Plants for a Southern Garden, asking for other favorites.
I put a little Poll on Dotty Pants Blog with a long list of my favs. Please Click on the Dotty Pants link, look on the righthand sidebar and check your favorites. Let's see what the top plants may be in addition to the ones Tom named.