Random Magic Weapons (any level)

This potent and feared enchantment allows the weapon to sever the heads of those it strikes. Upon a successful critical hit, the weapon severs the opponent's head (if it has one) from its body Some creatures, such as many abominations and all oozes, have no heads. Others, such as golems and undead creatures other than vampires, are not affected by the loss of their heads. Most other creatures, however, die when their heads are cut off. The DM may have to make judgment calls about this sword's effect. A vorpal weapon must be a slashing weapon.
Aura: Strong necromancy and transmutation
Caster Level: 18th
Requirements: Craft Magic Arms and Armor, keen edge, circle of death
Price: +5 bonus
Source: Dungeon Master's Guide v.3.5