Uni-Zombie - Zombies / Shiranui / Danger
There are a lot of different ways to build zombies, which makes the deck-building process very fun. This is a "pure" version, focused on milling, with a banish sub-theme featuring the Shiranui cards. My favorite part about this deck is how versatile and resilient it is; it can be very hard for your opponents to break your board, as you have multiple monster negates with Yuki-Onna, the Absolute Zero Mayakashi, Skeletal Dragon Felgrand Doomking Balerdroch, and even hand traps, destruction protection with Alghoul Mazera, battle protection with Yuki-Onna, the Absolute Zero Mayakashi, and Red-Eyes Zombie Necro Dragon.
Even if your board gets broken, you can come back with Red-Eyes Zombie Dragon Lord, Doomking Balerdroch, and Flying Mary, the Wandering Ghost Ship. You also have a lot of cards that allow you to get the best monsters from your opponents' field or graveyard, like Red-Eyes Zombie Necro Dragon, Vampire Fascinator, Dharc the Dark Charmer, Gloomy, Change of Heart, Zombie Necronize, and Snatch Steal, which you can use to cover your weaknesses or make The Zombie Vampire.
The best way to win against this deck is to stop it before it begins. The main problem in this deck is the lack of one-card combos, which can make it very vulnerable to disruption effects.
Card highlights:
Danger package (Danger!? Tsuchinoko?, Danger!? Jackalope?, Danger! Mothman!, Danger! Nessie!): I believe the danger package is underrated in this strategy. You can use Uni-Zombie's first effect to activate their effects. They can be used to unbrick hands while also extending plays and allowing easy access to Chaos Ruler, the Chaotic Magical Dragon, and Red-Eyes Zombie Dragon Lord. The only problem is that they don't work well with quick spells, but aside from that, they give you a huge advantage.
One for One: Can be used to summon Tearlaments Kitkallos with Magical Scientist and mill 8, Level Eater to go into link and synchro plays, or Glow-Up Bloom, to activate its effect in the graveyard after you activate Zombie World.
Painful Choice: I recommend choosing Necroworld Banshee, Level Eater, Changshi the Spiridao, Shinobi Necro, and Gozuki (or Mezuki, depending on your hand). What your opponent chooses doesn't matter much because you can discard it using Uni-Zombie anyway. Glow-Up Bloom is also great if you already have Zombie World (don't choose it with Necroworld Banshee, because your opponent can choose banshee and you won't be able to activate bloom). You can also consider Multi-Universe to keep your Zombie World safe.
Goblin Biker Grand Breakout: This is one of the few ways you can protect yourself from target negates on Uni-Zombie, while also greatly extending your plays by summoning Goblin Zombie, which you can use to summon Vulcarrion the Rotting Phoenix and continue.
Alternatives:
Burial from a Different Dimension: Good recursion tool that can also work as extension with Mezuki.
Twin Twisters: Can be a good alternative to Heavy Storm because of the discard cost.
Ghost Fusion, Ghost Sleeper, the Underworld Princess, Chicken Game, Upstart Goblin: Ghost Fusion is a good option extender because you can banish a Changshi the Spiridao and foolish a zombie. Those cards would work best in a list that allows the second effect to be activated more easily or that focuses more on fusion summons.
Super Polymerization, Garura, Wings of Resonant Life, Dragonecro Nethersoul Dragon: Another board breaker option that works well with the Ghost Fusion package.
Predaplant Verte Anaconda: Can be used in versions with Super Polymerization and/or Ghost Fusion to help rebuild and break boards in a grindy game.