Exit Wound: Weapons with the exit wound ability propel their ammunition entirely through living targets they hit. This effect deals an extra 1d6 points of damage. The weapon or projectile continues in a straight line beyond the original target. Targets in that path are attacked using the same attack roll as the original target; these additional targets gain a +4 bonus to AC for each previous target in the path. When an exit wound weapon or projectile hits an object, it stops. The exit wound can be applied to any ranged weapon; projectile weapons so enhanced bestow the ability on their ammunition.
Knockback: Knockback weapons often emit a low, almost inaudible hum when drawn. Whenever a knockback weapon hits its target, it initiates a bull rush attempt in addition to dealing normal damage. To resolve the bull rush attempt, treat the projectile as a Medium creature with a +8 Strength bonus. The projectile doesn't provoke attacks of opportunity, and it always tries to push the target as far back as possible. Only ranged weapons can have the knockback ability and they bestow it on their ammunition.
Come Here!Actually, wonder how the Returning property would work with the Harpoon...