Inspired by a creature in InuYasha, the corpse crow would probably make a great addition to your next undead / horror encounter.
Hit Dice: 1
Armor Class: 8 
Attacks: Bite (1d6), Burrow (1d4)
Saving Throw: 17
Special: Possession (see below), Immunities
Move: 4/18 (flying)
Challenge Level/XP: 5/240
Though not very tough, these creatures of nightmares are deadly foes and not to be taken lightly. Corpse crows survive by feasting on the corpses of their victims. A hit from a crow requires a saving throw to avoid having the crow burrow into the victim’s chest, consuming the heart. It will take a corpse crow 1 round per level or HD of the victim to burrow to the heart, and the burrowing can only be stopped by killing the crow. If the crow completes its painful advance or kills its victim before completion, the corpse crow gains possession and control over the victim’s body at half HP and -2 to attacks. If the body a corpse crow inhabits is destroyed, the crow will escape the body and seek a new victim.