Pilum – javelin used by Roman Legionnaires.

A Pilum (plural pila) was a javelin thrown by Roman Legionnaires to disrupt an enemy line moments before closing for hand-to-hand contact.
The pilum was about 6 or 6 1/2 feet long, weighing between 2 and 5 pounds (heavier early in Roman era, lighter later). There was an iron shaft at the front which was about a quarter inch diameter and about 2 feet long. A wood pole, 4 feet long or so was attached to the metal shaft. The wood added plenty of mass to the pilum giving it good penetration capacity. A point on the base of the pilum made it usable to stack with other pila in camp or plant in the ground for an ad hoc defense from cavalry.
A hard triangular tip was designed to punch through armor. With enough force it could penetrate a shield.