Vampiric

Vampiric — A weapon with this property restores two hit points to its wielder — up to the wielder's maximum hit points — whenever the weapon draws blood from another creature. Only a weapon able to deliver piercing damage may have this property. While wielding or carrying a Vampiric weapon, the owner enjoys a +4 bonus to saving throws against undead. On a critical miss, the weapon's Vampiric property is suppressed for the next 1d4 rounds. On a critical hit, an injured foe will bleed for an additional two points of damage per round for the remainder of that encounter, or until healed. This extra bleeding damage doesn't cause the Vampiric weapon wielder to regain two hit points.