Forbidden Cards
A card so powerful, no one knows what it does.
Pot of Greed.
A lady yiffs a dragon because she hates god.
Branded
This card was never reprinted because of copyright infringement.
Elemental Hero Air Neos
This card was banned due to the amount of card advantage you would gain from special summons.
Maxx "C"
Who's turn is it?
Tearlaments
This player won a tournament because no one knew what his deck did.
Dinh Kha Bui with Prank Kids
Even after an errata, this card was still broken.
Imperial Order
KABOOOOMMMMMMMM
Ryzeal
This new change in the official tournament rules caused a major upset in the community and changed the procedures of the match.
New Time Rules
This was a prominent card during the height of JUHU format that prevented you from summoning monsters that weren't of the same archetype.
Artifact Mjolnir
Jail Bait
Traptrix
This player was involved in a controversial yet legal tactic by misleading a player with a gentleman's agreement.
Patrick Hoban
One of the strongest floodgates ever printed. This spell card defined a format.
Mystic Mine
The less they make sense, the more they're winning.
Ojamas
This change completely changed how the game was fundamentally played, causing players to leave the game. This change was eventually revised.
Master Rule 4