Long weapon
The spear and halberd appears as a usable weapon in Assassin's Creed II, but you can only acquire it through countering. Also once combat is over or if you sprint away Ezio will discard it. Spears and halberds can be broken in half by an opponent but would still be usable and would be held in two hands (bottom of spear/halberd in left hand, top of spearhead/halberd with spearhead in right hand).
Special Attacks
In combat training, it is possible to learn a special attack for each the spear and the halberd.
The special attack of the spear sweeps surrounding guards off their feet, leaving them open for an easy kill or quick escape.
The special attack of a halberd is an unblockable attack that does extra damage to an opponent (normally a one-hit kill). However, this attack takes longer than a normal attack, leaving you open to attacks and counters if surrounded.