Halberdier

A halberdier is a military unit. 
They are soldiers armed with a long polearm known as a halberd, and are usually utilized in the anti-cavalry role and sometimes phalanx fighting formations. The halberd is far more effective and useful than its distant cousin, the pike. It consists of a long wooden pole (about 10+ feet long) with an axe head mounted to one side of the weapon and another implement, usually a metal spike, mounted to the opposite side.
With this lethal combination, a halberdier could not only stab a horse or impale its rider, but also dismount the cavalryman, parry and block other polearms, or hamstring the rider's mount. Many armies and nations in Middle-earth realized its effectiveness and thus trained special units to wield the halberd, known as halberdiers.
=== Mordor ===
The armies of Mordor were the greatest exponents of this weaponry, and their influence passed it on to other allies serving under the thumb of Sauron. However, these weapons were anything but fine smith-craft; they more or less resembled a rusted pruning hook horribly blighted by the corrupting influence of the Dark Lord. The basic halberd design encompassed a bewildering array of variants in Sauron's army, as seen when the Orcs under Gothmog kneel with their weapons in a vain attempt to stem the onrushing deluge of Rohirrim horsemen on the Pelennor Fields in the Return of the King movie. Despite the near-total annihilation of the Mordor-host by the cavalrymen of Rohan, the Orcish halberdiers appear to have taken down a few of their vaunted mounted enemies.
=== Isengard ===
The Uruk-hai of Saruman also appear to utilize the halberd, alongside the more numerous pike. Several can just about be made out during the Battle of the Hornburg, being utilized by Saruman's Dunlending allies as well. These, in addition, also resemble more of a rusty pruning hook than a worthy weapon to be used in combat.
=== Rhûn and the Harad ===
Serving for many years alongside the halberd-loving armies of Sauron, the soldiers of Rhûn and the Harad appear to have adopted the habit as well. In the Two Towers movie and book, the army of Easterlings marching into the Black Gate wield clearly visible halberds and other polearms.
The Rhûnic halberd retains the ash pole wielded by its Gondorian adversaries, but has other, distinct features as well. For one, each appears to be a finely-crafted work of masterful craftsmanship, not a pruning hook. Instead of a smooth, keen axe head edge, the Easterling halberd possesses a heavily serrated edge designed to rend bone and flesh. The standard spear point tops the pole, while a steel spike protrudes from the opposite side of the axe head. Aside from the armies of Mordor, the Rhûnic soldiers were the best exponents of this superb weaponry.
The Haradrim also utilized these weapons, though not on such a massive scale as their Easterling and Orc companions-in-arms. Several of their soldiers, riding upon the mumakil at the Pelennor Fields, wield halberd-like polearms. It can thus be assumed that a fair amount of their brethren utilized these weapons as well.
=== Gondor and Rohan ===
The Free Peoples of Middle-earth also used halberds, though on a much lesser scale than their adversaries. Several soldiers of Gondor, seen in Minas Tirith, wield halberds instead of pikes. During the sack of Rohan in the Two Towers movie, the hastily-assembled Rohirrim militias also appear to have used crude halberds in a vain attempt to halt the Uruk-hai advance.