Favored weapon

When you take your first level in a divine class (i.e. Cleric, Favored Soul, and Paladin),you get to choose a deity. Each deity has one favored weapon; as you take additional divine levels, you might get additional benefits.

Default favored weapons
Depending on your race, you can select one of the following: Bastard Sword, Dagger, Greatsword, Heavy Mace, Longbow, Longsword, Maul, Quarterstaff, Scimitar, Shortsword, Sickle, Warhammer

(The Forgotten Realms races are the three iconics included in higher tiers of the Shadowfell Conspiracy expansion - Morninglord. Shadar-kai and Purple Dragon Knight. Everything else counts as an Eberron race.)

Additional favored weapons
Certain abilities allow you to add another weapon or weapon group as an extra favored weapon.
 * Dwarven Waraxe: Racial Enhancements Dwarf - Dwarven Weapon Training Tier 3
 * Rapier, Falchion, Shortbow: Racial Enhancements Wood Elf - Faith of the Forest Tier 3
 * Longsword, Battle Axe, Heavy Mace, Morningstar, War Hammer: Paladin Enhancements Knight of the Chalice - Adept Combatant Tier 2
 * Greatsword: Paladin Enhancements Knight of the Chalice - Holy Combatant Tier 3
 * Heavy Crossbow, Light Crossbow: Universal Enhancements Inquisitive - Divine Inquisition Tier 4
 * Longsword, Longbow, Shortsword, Scimitar, Heavy Mace, Quarterstaff, Bastard Sword, Sickle, Warhammer, Maul, Dagger, Greatsword (select one): Epic Destinies Divine Crusader - Axiom of Faith Tier 3

Misc
 * Warforged and Bladeforged treat (quarterstaff) as their favored weapon.
 * Weapons with the Favored Weapon enchantment are favored weapons for everyone.

Abilities that require favored weapons
Certain abilities require that you wield a favored weapon in your main hand.
 * War Soul enhancements and Warpriest enhancements
 * Dark Apostate enhancements
 * Divine Crusader epic destiny