Currently, mobs like zombies and skeletons can equip (custom) wands and guns, but they will simply use it to deal melee hits rather than shooting with it. Letting them use wands and guns 'wisely' could be interesting. But, unless the gravity is very small, aiming could be different. (And unless the bullets are fast, the motion of the target should be taken into account.)

This has been implemented in KCI 12