I have had (and still have) Springer's, Azure's, Yellow tails (C. parasema), Allen's, and Starki's - the least aggressive would have to be the Allen's and the Starcki's - the first three I listed have all showed significant aggression with maturity, but not as much as the more aggressive species such as blue devils.
I should note that my damsels (except the Starki) currently reside in a 40B (w/ 20L sump) with a total of 15 fish (seven damsels, 2 clowns) - sort of like slightly crowding African cichlids to cut down on territorial aggression. They leave a red firefish, elongate pseudochromis, and Lubbock's fairy wrasse completely alone.