According to Vetron's Guide to Weapons and Armour, the halberd has a "10" effectiveness rating, making it one of the strongest weapons.
Halberds have been seen in the series since Ultima IV. From that point onward, their function and high damage stayed the same. Indeed, in Ultima V it was even possible to attack through walls with it. They were planned to be in Ultima IX, but ultimately dropped, apart from some decorative ones.
Seven feet of stout wood topped with a blade of deadly steel. The halberd requires excellent coordination to be used effectively. It is the most deadly of weapons in the hands of an expert, who uses it to strike over the heads of his fellows. A favorite among Paladins.
Polearms require much strength to wield but they're extremely effective. Most popular among those strong enough to wield it is the halberd, a long stout staff with a battleax blade at the end that allows its wielder to strike a foe at twice the distance of most weapons.
A polearm is generally a stout wooden or metal staff topped by a metal cutting or bludgeoning fixture. Morningstars, halberds, and other polearms are prized for the damage they are capable of doing and for their long reach. Unfortunately, polearms are unwieldy weapons which are most effective in the hands of a user possessed of great strength and dexterity.