The Dane axe (or Danish Axe) was a fearsome, two-handed axe with a broad, heavy head and a 3 to 4 foot haft. The sheer size and weight of this weapon made it one of the most powerful weapons on the field until the development of cavalry. Handled with skill, the Dane axe could shatter a shield (and likely the arm behind it) with a single blow. Armour was a poor defense, since plate armour had not been developed, and, even if maille withstood the blow, sheer inertia could cause terrible crushing injuries.
Commonly used by Vikings, Anglo-Saxon Housecarls and The Varangian Guard, Dane axes were popular weapons up until the advent of mounted cavalry led to the decline of the Alfred the Great-style shieldwall.
One legend of the Battle of Stamford Bridge is of the berserker who, armed with a Dane axe, held the bridge alone, and was only killed when an English soldier speared him through the planks of the bridge itself, suggesting that no-one could stand against a well-wielded Dane axe, rather they must it by stealth.
Ceremonial weapons might also be made of these weapons, but might have even longer hafts and be decroated with inlays of silver etc.