Headless Rider

Whenever Headless Rider or another nontoken Zombie you control dies, create a 2/2 black Zombie creature token.

Hordewing Skaab

Flying
Other Zombies you control have flying.
Whenever one or more Zombies you control deal combat damage to one or more of your opponents, you may draw cards equal to the number of opponents dealt damage this way. If you do, discard that many cards.

Curse of the Restless Dead

Enchant player
Whenever a land enchanted player controls enters, you create a 2/2 black Zombie creature token with decayed. (It can't block. When it attacks, sacrifice it at end of combat.)

Necroduality

Whenever a nontoken Zombie you control enters, create a token that's a copy of that creature.

Diregraf Colossus

Diregraf Colossus enters with a +1/+1 counter on it for each Zombie card in your graveyard.
Whenever you cast a Zombie spell, create a tapped 2/2 black Zombie creature token.

Don't Have

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch.

Endless Ranks of the Dead

At the beginning of your upkeep, create X 2/2 black Zombie creature tokens, where X is half the number of Zombies you control, rounded down.