Lightning Spear is one of the few offensive miracles and also one of the only spells that inflict lightning damage. It features a long casting time, pin-point accuracy, and a very long effective range (a good deal longer than lock-on range, although manual aiming can be tricky).
As with most other miracles, Lightning Spear scales with Faith level and the type of Talisman it is cast by. Throwing Lightning Spear and its variants into water will cause lightning damage to radiate from the point of impact.
Lightning Spear is a good long-range way of greeting enemies. It deals respectable damage and can be used often thanks to its generous amount of uses. Lightning Spear deals lightning damage, which helps diversify the types of damage a player can deal.
In PvP, Lightning Spear is risky to use due to its long casting time and its lack of AoE damage without hitting a body of water which aren't very abundant. However, it deals good damage if it connects due to the lower lightning resistance most players possess. In any situation, Great Lightning Spear is superior due to its greater damage and no drawbacks.
Using a bow or binoculars' zoom-in feature to manually aim slightly to the left of a stationary target and then using lightning spear can ensure accuracy against targets not within lock-on range. Bows are more useful for the task as their zoom-in has a crosshair.