All units listed below benefit from Parthian Tactics. The Camel Archer (denoted with a *) does profit from the armor and attack increase Parthian Tactics grants, but the Berbers do not get Parthian Tactics. Hence, this is only relevant in games with Full Tech Tree checked.
"The horse archers of Parthia, now part of modern Iran, were renowned for their ability to shoot arrows at pursuers, whether the archers were in real or feigned retreat. Being able to shoot at enemies while withdrawing was very irritating to the enemy, especially when pursuers were too slow to close the gap. Although the Parthians were an ancient people, their tactics were adopted by later civilizations that employed horse archers and their name remained attached to the maneuver. The phrase “parthian shot” has come to mean any comment made while exiting a discussion."