Regarding the Terran Raven unit, and its Point Defence Drone (PDD), what unit attacks will be intercepted by the PDD?
I haven't been able to find a complete list.
Taken from the Starcraft Wikia:
The drone intercepts missiles and projectiles fired by certain enemy units and buildings. According to the in-game description of the point-defense laser it is effective against marauders, vikings, banshees, battlecruisers, thors, missile turrets, stalkers, phoenixes, photon cannons, queens, mutalisks, corruptors, hydralisks, and spore crawlers.
Its defensive abilities use up 10 energy per shot. Units like vikings and phoenixes that attack twice or more per cycle will drain 10 energy for each of its individual attacks (i.e. 1 viking attack consists of 2 missiles. 20 energy would be consumed to intercept both missiles).