From LSWiki

Class: Ranged Weapon Skills
Attribute: Dexterity
Pedagogy: Physical Training

The ability to throw weapons in combat.  If one is throwing, for instance, a dagger, 
one is using both this skill and one's dagger skill.  When throwing weapons, this skill 
influences the speed, accuracy, and effectiveness of one's attacks.

Trainers

Avalon: Bercilak
Wandering Lhethan Hagal
Losthaven: The Grey Mouser
Losthaven: Raelan Jax
Skarlan: Badlokk
Shatterspire: Sthlar
Valathyr: Mitandim
Association required:
Losthaven Guard: Terethrond
Guild required:
Aisenshi: Musashi
Justicars of Tyr: Edwin
Justicars of Tyr: Strom Thromgald
Knights of the Round Table: Sir Lancelot
Nizari: Hasan Wanders
Ordo Ignis Aeternis: Aedryl 
Ordo Ignis Aeternis: Iklam wanders in Northlands
Ordo Ignis Aeternis: Itozuma wanders in Quetlatl
Quest required