"Wind-Up Magician" and "Wind-Up Juggler" and in the artwork of "Zenmairch".
"Wind-Up" (ゼンマイ Zenmai) is an archetype of wind-up toy-like monsters that premiered in Generation Force and received further support in Photon Shockwave and Order of Chaos. There are monsters of all Attributes, though EARTH is most prominent, and 4 Xyz Monsters.
The effects of known "Wind-Up" monsters ranging from Special Summon and swarm tactics to Level and ATK manipulation to obtain benefits. Each non-Xyz "Wind-Up" monster can only use its effect once while face-up on the field ("Wind-Up Shark" and "Wind-Up Honeybee" are the only exceptions so far). Many cards that support them revolve around flipping down or otherwise recycling.
A "Wind-Up" Deck uses a variety of single-use monster effects to control the field while "Wind-Up Factory" generates hand advantage. You can use "Tour Guide From the Underworld" to Xyz Summon "Wind-Up Carrier Zenmaity" (Traditional Format only) and proceed to Summon whatever you need from your Deck. "Wind-Up Soldier" can change its Level to 5, allowing you to use "Cyber Dragon" or "Instant Fusion" to produce Rank 5 Xyz Monsters. "Wind-Up Kitten" works with "Junk Synchron" for Level 5 Synchro Summons.
"Wind-Up" is an excellent Deck for Xyz Summons, taking advantage of easily increasing their Levels with "Soldier", "Wind-Up Warrior", "Wind-Up Dog" and "Wind-Up Shark". Summoning any of the first three and then Summoning "Shark" allows for an easy Rank 5 Xyz Summon, using cards like "Wind-Up Arsenal Zenmaioh" to break Set monsters and Spell and Traps, "Number 61: Volcasaurus" and "Adreus, Keeper of Armageddon" to destroy any opponent's face-up monster (and, in the case of "Volcasaurus", deal massive damage) which you couldn't beat with ATK alone, or provide a monster which can survive a surprise "Mirror Force", in the form of "Tiras, Keeper of Genesis". If dominating, "Digvorzhak, King of Heavy Industry" is also an option, allowing destruction of up to 3 cards, but due to it needing quite some material, most Rank 5 Xyz Monsters outclass it, due to the amount of effort lost when it meets cards like "Bottomless Trap Hole". "Shark Fortress" can provide both protection to more vulnerable low-ATK Xyz Monsters such as "Carrier Zenmaity" or "Number 16: Shock Master" and increased OTK potential through its double attack effect.
Any Rank 4 Xyz Monster can also easily be Summoned by the combo of "Shark" with any of the Level 4 monsters, and due to the speed, allows 3 material monsters like "Vylon Disigma", and "Numbers" "10", "16", "32" and "69" to be Summoned without loss in card advantage.
"Wind-Up Rat", "Carrier Zenmaity" and "Wind-Up Hunter" can produce a loop that can result in your opponent sending from 2-6 cards from their hand to Graveyard. First, you must have "Hunter" in your Graveyard. Then, you must have "Carrier Zenmaity" on the field, and activate its effect to Special Summon a "Rat". Then activate the effect of "Rat" to Special Summon "Hunter" from the Graveyard. Use the effect of "Hunter" to Tribute "Carrier Zenmaity" and make your opponent send a random card from their hand to the Graveyard. Then use "Rat" and "Hunter" as Xyz Materials to get another "Carrier Zenmaity", and then repeat the loop twice by sending "Hunter" to the Graveyard to Special Summon another "Rat".
However, due to limitation of "Carrier Zenmaity" in September 2012 Lists, most "Wind-Up" Decks have switched goals from depleting an opponent's hand to Xyz Summoning numerous Xyz Monster (mostly Rank 3 and 5's) in just one turn using cards like "Wind-Up Magician" and "Shark", bolstered with "Wind-Up Factory" to finish off the opponent (possibly in that same turn) or deny them options through cards like "Shock Master". The incredible swarming power of the Magician-Shark combo allows the "Wind-Up" player to swarm the field with many different combinations of Xyz Monsters to answer any threat, often ending the game right then and there. This tactic is no longer possible with "Carrier Zenmaity" banned and "Magician" limited in the March 2013 Lists.
"Wind-Up Factory", "Carrier Zenmaity" and "Honeybee" can provide you with single-use monsters to address any situation. You can toolbox "Soldier" to kill low-Level beatsticks, "Juggler" to break walls, "Kitten" to deal with Extra Deck monsters and defuse Flip Effects, "Rat" to produce Rank 3 Xyzs, "Rabbit" for reuse and deflection, or "Knight" for defense. This is no longer possible in March 2013 Lists, as "Carrier Zenmaity" is banned.
With "Carrier Zenmaity" banned and "Magician" limited in March 2013 Lists, there is another way to OTK is by using "Zenmairch" alongside "Zenmailstrom", and utilizing "Soldier" and "Knight". Having both "Soldier" and "Knight" on the field, along with activatable "Zenmairch" and "Zenmailstrom" on the field is needed, together with either another "Knight" or "Soldier" in the hand. The combination lands for at least 9000 damage, but 9400 with an activated "Soldier".
While a very strong Deck theme as of the September 2012 ban list, it is not invulnerable and can be slowed or temporarily interrupted long enough to be defeated.
For "Wind-Up" Swarm players, cards that counteract field swarming or effects like "Torrential Tribute", "Maxx "C"", "Effect Veiler", "Needle Ceiling" and even "Summon Limit" and "Summon Breaker" can stop the swarming chains if activated at the right time before they become too devastating. And due to most "Wind-Up" Decks being composed of different Types and Attributes (much like "Gladiator Beasts"), both "Rivalry of Warlords", "Gozen Match" and "Battle of the Elements" can stop this Deck effectively.
In more specialized Decks both "King Tiger Wanghu" and "Skill Drain" can also hinder the "Wind-Up" Deck synergy very well, either by stopping many of the weak "Wind-Up" monsters from staying on the field long enough to activate their effects (including "Wind-Up Rabbit", which is destroyed before it can save itself upon being Summoned) or by just outright stopping all effects from resolving on the field (but "Rabbit" can still be activated however as it resolves in the Banished Zone).
"Prohibition" and "Psi-Blocker" can also slow down a "Wind-Up" Deck if you correctly call "Wind-Up Magician", "Wind-Up Rat" or "Wind-Up Shark" proactively at the right time to hinder your opponent's Deck options. In an opposing Deck with a high number of WIND-attribute cards, "Mystic Fairy Elfuria" is also very effective at stopping almost all of the preferred Xyz Summoning options available to a Wind-Up Deck if Rank 3, 4 and 5 Summoning is blocked.
"Light of Intervention" can be a peculiar choice against "Wind-Up"s as it can halt them from being flipped face-down (i.e. via "Wind-Up Zenmaister", "Legendary Wind-Up Key" and "Book of Moon") in the hopes of re-using their effects.
Finally "Chain Disappearance" is an excellent way to remove the threats of "Magician" and "Rat" from being recycled repeatedly by your opponent.
- An actual wind-up toy is wound up (Summoning it), does what the toy was made to do (activating the effect), then is completed (effect can only activate once). Returning to hand or flipping it face-down and back up signifies "winding-up" the monster.
- All "Wind-Up" cards with "発条, Zenmai" are spelled "Zenmai" in their TCG names.