Firebomb

Firebomb is a Fire spell used by Witch Doctors in Diablo III.

In-game
Hurls a burning skull that explodes for Fire damage within 8 yard radius. The skulls may be thrown over the obstacles and enemies (including Waller affixes, but not solid walls), and do not count as missiles.

Bombs have limited throwing radius, roughly 60 yards, and can only be hurled at visible locations.

Runes

 * Flash Fire: No longer explodes, only damaging one enemy, but can bounce to up to 6 additional enemies within 25 yards. Damage is reduced by 15% per bounce.
 * Roll the Bones: The skull can bounce up to 2 times in the same direction as it was initially hurled, exploding each time with full power. Bouncing distance is roughly 15 yards.
 * Fire Pit: The explosion also creates a pool of fire that deals additional 60% damage as Fire over 3 seconds. Multiple pools in one area stack.
 * Pyrogeist: Instead of regular explosions, creates a column of flame that spews fire at one closest enemy, dealing a total of 880% damage as Fire over 6 seconds. Only 3 Pyrogeists can be active at a time.
 * Ghost Bomb: Damage type changes to Cold. In addition to the base explosion, releases a larger blast that deals an additional 30% damage as Cold within 28 yards radius.

Non-rune enhancements

 * Simplicity's Strength (Legendary Gem): increases damage by 25% (+0.5% per rank) and heals the character for 4% of maximum Life per hit (rank 25 bonus).
 * Boyarsky's Chip (Legendary Gem): Taunts the first enemy hit for 2 seconds (rank 25 bonus).
 * Mordullu's Promise (Legendary Axe): each cast restores 100-125 Mana.
 * Depth Diggers (Legendary Pants): damage increases by 80-100% (when equipped with Mordullu's Promise).
 * Helltooth Harness Set (Set Bonus for 2 items): damaging enemies with Firebombs will apply Necrosis, slowing enemies by 60% and inflicting 3000% damage per tick for 10 seconds. Elemental Damage type is chosen from the highest skill bonus of the character.
 * Helltooth Harness Set (Set Bonus for 6 items): after casting Wall of Death, gain +9000% increased damage for 15 seconds for Firebomb.

Passives

 * Vision Quest: every damaging hit increases Mana regeneration by 40% for 5 seconds, effect does not stack.

Trivia

 * The spell seems to involve some sort of fire spirit (like Bone Spirit), not just a flammable substance, since a flaming figure is briefly visible overhead when the skull explodes.

Development
Originally, this skill was named the Skull of Flame.

Prior to patch 2.3, it was the only Witch Doctor primary skill that couldn't change its damage type.