Often considered mechanically inferior to other options for managing combat, there is a strong case to be made for certain Equip cards beyond the standard Premature Burial and Snatch Steal.
Most decks mainboard these cards, and both of them increase your access to another card type entirely: Monsters. Neither of them act as a traditional Equip card, which modifies the ATK and/or DEF of the Monster it is equipped to or grants it another effect.
Why Not Equips?
First, let's go through mechanical weaknesses that prevent Equips from being seen as a successful card type. Equips by default are combo cards that depend on you having a face-up monster you can attach it to, this makes for weaker topdecking and easier disruption of your strategy. Equips must remain attached to your monster to remain impactful, their effects disappear when they leave the field. Equips also usually rely on the Battle Phase to earn their keep. The phrase "MST on attack declaration." sends chills down the spine of the Equip user. Book of Moon and Tsukuyomi have a presence in the format and flipping a monster face-down always destroys the Equips attached due to mechanics, rather than card effects, meaning Blast With Chain will not trigger. Unless you win two battles, Equips are at best an even trade and at worst a net minus in terms of card advantage. In most cases, "one-for-one" removal cards like Smashing Ground are more reliable. Yet, there are decks that succeed using them, mainly Warrior variants like Ben Kei OTK or Double Tap Warriors. These decks typically succeed by condensing damage into fewer turns through the use of multiple attacks per battle phase, empowered by Equip cards. These attacks are features of specific monsters, like Armed Samurai - Ben Kei and Mataza the Zapper.
Gearfried is another Warrior variant that uses Equips, but mainly so Gearfried the Iron Knight can destroy them and trigger their effects. I prefer the hand control offered by Smoke Grenade of the Thief to the damage boost and potential Raigeki Break effect associated with Blast With Chain; Blast is much slower than Smoke Grenade. Smoke Grenade is tutorable through Iron Blacksmith Kotetsu. A ratio of 3 or 4 targets to 1 searcher would be appropriate for Kotetsu, and by default we'll probably have two stellar cards to fetch from the deck at least. Since Smoke Grenade of the Thief warrants running as a three-of, Kotetsu may be a two-of or even three-of. A deck featuring him would need to deviate from the standard Warrior formula significantly however, as blanking opposing Nobleman of Crossout would no longer be possible.
Outside of the decks described above, what is the use case for cards this mechanically bad? Obviously, you use the best of them. A Sakuretsu Armor destroying the monster you just spent an Equip card on feels really bad and decks run those in threes. Since most Equips are Spells, they play nicely with Jinzo and Royal Decree. Equips generate value as burn cards, increasing the amount of damage being done to LP, and/or as removal, helping your monsters run over your opponent. So, technically speaking, that's not nothing.
The best ATK or DEF modifying Equips In descending order of maximum power, from left to right. United We Stand has been utilized to punish Ojama Trio in the Panda Burn matchup, in addition to appearing in every deck that might think about using Equips. Mage Power has edge case advantages over UWS, powering up more quickly and having synergy with Solemn Judgment and by extension, Blade Knight. Axe of Despair is the most consistent, offering a flat, massive, 1000 ATK boost. Axe's other properties: being treated as an "Archfiend" card, and its tribute to return it to the top of the deck when it would otherwise hit grave; both are pretty irrelevant to most decks.
The Big Bang Shot + Asura Priest combo versus a field of sheep tokens is a well known game winning play. Big Bang's most nefarious uses, however, are defensive. Change your Spirit Reaper to defense mode or activate Scapegoat and put a Big Bang on the opponent's monster. Because you control the Big Bang Shot, your opponent will take all piercing battle damage they inflict to you. Another good reason to put Big Bang on a monster you don't control is its removal effect--when Big Bang leaves the field the equipped creature gets banished. Combos excellently with Giant Trunade and Abyss Soldier. The Spell's +400 ATK gets any 1700+ATK monster the ability to clear a Gravekeeper's Spy while putting your opponent on a four turn clock if all they have is sheep tokens.
Wicked-Breaking Flamberge - Baou is a rarely seen card that provides the Dark Ruler Ha Des/Dark Balter the Terrible monster effect negation ability while also providing +500 ATK to make sure that the range of monsters that can be destroyed is wide enough to include most things in defense mode (and plenty in attack mode too). The Flamberge's steep cost of needing an additional discard makes this tech most suitable to decks that really like cards in grave or have access to virtual card advantage, like Turbo Chaos or Bazoo Return.
Megamorph - is commonly seen in decks that use either Cyber-Stein or Injection Fairy Lily for obvious reasons; can be used as a Spell Speed 1 Shrink in a pinch.
Neat, But Are You Really Gonna Run That?
Metalmorph is how a Mystic Tomato can topple a Black Luster Soldier - Envoy of the Beginning.
Fusion Sword Murasame Blade's primary application is to be equipped to Gearfried the Iron Knight, which takes him to an outstanding 2600 ATK. Unboosted Blade Knight becomes 2400. Not too shabby if you need to run over a Chaos Sorcerer.
Autonomous Action Unit is too expensive and too high-variance for the mainboard but could have applications for the sideboard vs monster-heavy lists.
If your offense is missing some spice, consider some monster-focused solutions. They can pay off over time and also shorten the amount of time needed to win the game. Stay wary of removal, and try to win the game with the extra damage/unique effect before the opponent can mount a response.
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