Revival Spell
Swordsoul Sacred Summit
This continuous spell sees some play in Mekk-knights as a way to draw off a mekk-knight summon
Phoenix, Cerberus, Unicorn
Knightmare
Number 101: Silent Honor ARK
Number C101: Silent Honor DARK
This card has special abilities "that weren't even written on the card," such as Instant Attack and Point-to-Point Transfer
The Winged Dragon of Ra
This thunder monster has seen heavy side deck use as an anti-backrow normal summon.
Denko Sekka
An old zombie revival spell, this card grants new life by taking it from your opponent's GY.
Book of Life
Forbidden for a brief period, this xyz monster was critical to the fusion sub zoodiac combo.
Daigusto Emeral
Mandrake, Nightshade, Holy Angel
Trickstar
Number 69: Heraldry Crest
Number C69: Heraldry Crest of Horror
Known for its amazing floodgate and hand control effects in the TCG, this fusion monster didn't have an effect when it was first revealed in its manga
Masked HERO Dark Law
Released as a secret rare in Galactic Overload, this card saw use in a wide variety of decks that just needed a few extra cards
Cardcar D
Black Garden
This card received hype for a brief period when it was rumored Konami was increasing the starting Life Point total.
Ancient Leaf
Crowley, Endymion, Vahram
Magistus
Number 9: Dyson Sphere
Number C9: Chaos Dyson Sphere
In Yu-Gi-Oh GX, this card was originally a fusion monster, but was printed as an effect monster in Crossroads of Chaos
Neos Wiseman
Of the 3 prize card Darklords, this is the only one that cannot be Special Summoned at all
Darklord Desire
In the anime, this was an actual custom card that Pegasus made real.
Ayers Rock Sunrise
Of the counter traps that have effects that draw cards, this is the only one that lets only you draw.
Stellarnova Alpha
Leo, Basilisk, Unicorn
Heraldic Beast
Number 96: Dark Mist
Number c96: Dark Storm
In the anime, this monster could be revived from the graveyard by discarding a trap card, thereby giving it an extra 1000 ATK points.
Uria, Lord of Searing Flames
Originally released as a prize card, this is one of the few cards in the game with a mandatory negation effect.
Doomcaliber Knight
Let's go play some games with Rabby.
Melffy Tag
Capshell
Opening, Condemnation, Bond
Branded
Number 102: Star Seraph Sentry
Number C102: Archfiend Seraph
In the manga, this synchro card was a tuner monster, though that was removed in the TCG.
Stardust Spark Dragon
Originally debuting as a Secret Rare in 2007, this card was the cover card for an OCG structure deck never released in the TCG
Diabolos, King of the Abyss