Random Magic Weapons (any level)

A dancing weapon can be loosed (requiring a standard action) to attack on its own. It fights for 4 rounds using the base attack bonus of the one who loosed it and then drops. It never leaves the side of the one who loosed it (never straying more than 5 feet) and fights on even if that creature falls. The wielder who loosed it can grasp it while it is attacking on its own as a free action, but when so retrieved it can't dance (attack on its own) again for 4 rounds.
Aura: Strong transmutation
Caster Level: 15th
Requirements: Craft Magic Arms and Armor, animate objects
Price: +4 bonus
Source: Dungeon Master's Guide v.3.5