Thought of this to go with the monster I posted last night, but can be applied to make any undead more interesting.
1. Maggot Cloud: waves of the insects pour forth from the wound obscuring vision. Everyone within the area not undead is at -1 to hit per round, area 5' per round, max -3 to hit and 15'. All food in the area is spoiled. Lasts til Zombie killed.
2. Animating Fire: The magic animating this thing bursts forth from its wounds as fire. 1d6 damage to the striker, Save VS Breath Weapon for half.
3. Independent Bits: on a critical hit or taking 5 damage from one hit, one it its limbs separates and attacks on its own. It has 3 HP.
4. Curse of Age: Anything touching the undead is aged to the moment when it originally died. Swords become old and brittle, limbs wither and rot off, arrows crumble to dust. Luckily, it takes the damage first.
5. Light of the Next World: Blinding light pours from it's wounds. After the first successful hit, attackers get +2 to hit it. 2nd successful hit: -2. 3rd Successful hit: attackers are effectively blinded until it is killed.
6. Death's Flatulence: gasses pour forth from the wounds. Everyone within 10' must Save VS Poison or retch for the round after it is struck.
7. Necrotic Blood: The attacker must Save VS Poison or the blood of the Undead causes festering wounds that do 1 point of damage per round. A Save VS Breath Weapon can be used in following rounds to avoid the spray.
8. Master of Grime and Space: Everyone striking the undead in the first 1d4 rounds of combat must Save VS Spell or be teleported to a pre-set location, probably where its master is.
9. Transfer of Control: The attacker Saves VS Spell or is now under the Necromancer's command. The Undead begins attacking at random. The attacker can Save again every time he/she takes damage.
10. Disgusting Target: The attacker must Save VS Horror or suffer an effect on the Horror table from Tales of the Grotesque and Dungeonesque