Okay, I'm starting the errata list. This list is for cards which have vague wording, or whose effects disrupt the mechanics of the game. I'm also planning to errata cards which are broken based on the number of turns they require to activate. You'll also notice that I double posted. Oh, well. Post count is disabled anyway.
Wario: If this card remains face up on the field for three of your turns, destroy all monsters on your opponent's side of the field.
Mr. Game and Watch: When this card is flip summoned successfully, change this monster to defense position. Mr. Game and Watch's battle position cannot be changed for three turns. For three turns, Mr. Game and Watch cannot be destroyed by the effect of monster, spell, or trap cards.
Link X: This card can be special summoned. To tribute summon this card, you must sacrifice one Link card on your side of the field.
Groudon: This card can be special summoned. To tribute summon this card, you must sacrifice monster on your side of the field while Pokeball is active.
Phazon Suit Samus: Phazon Suit Samus is not affected by spell cards.
Kirby: (Kirby gains the monster's current atk/def, not printed atk/def.)
Abra: Select one opponent's monster and switch control of it with this card. This effect cannot be used during the damage step.
Spare Stock: Select one monster from your graveyard. Add the selected monster to your hand, or special summon the selected monster to the field in face-up attack or defense position.
Star: Raise one monster's attack by 1000. After three turns have passed, send this card to the graveyard.
Warp Star: Tribute one monster on your side of the field. Inflict direct damage to your opponent's life points equal to the defense of the tributed monster.
Cracker Launcher: (I tested this, it's broken with it's original effect.) Every three of YOUR turns this card remains face up on the field, destroy one monster on your opponent's side of the field. If your opponent has no monsters on his/her side of the field, destroy one of your opponent's spell, trap cards.
Item Snatch: Select one spell or trap card on your opponent's side of the field. Send the spell or trap card to your side of the field.
Consume: Equip this card to Kirby. While this card remains face up on the field, once per turn, during your main phase, you may select one monster on our opponent's side of the field. Kirby's atk/def become that of the selected monster.
Yoshi's Island: Every two turns this card remains face-up on your side of the field, you gain 200 life points. In addition, all monsters currently on your side of the field gain an additional 200 defense. (Essentially, monsters played after this effect "goes off" do not get the 200 def boost. I'm guessing that was the creator's intention, but he/she left it vague)
Reverse
This card is really bad. Reverse it's effects. Somebody's going to have to come to a consensus about what that means. Does it mean that you get to play the spell instead of them? Does it mean that atk/def increases become decreases and vice-versa? Does it mean that the spell card Macbeth affects traps instead of spells? For example, if I play Star, and you play reverse, does my star decrease my monster's attack, or do you get to select a monster that you control and increase its attack? I recommend that we don't use this card until somebody figures out what "reverse its effects" means)
Barrier: Your opponent cannot declare an attack this turn.
Wavedash: Activate when an opponent's monster declares an attack on a monster you control. Negate that attack.
Second Chance (continuous trap card): Monsters on your side of the field cannot be destroyed in battle if the monsters' atk are equal.
Scan Visor: Flip all or your opponent's face-down cards face up. Flip effects are not activated. If a spell or trap card is flipped face-up, it is not activated. Then, return all non-continuous spell or trap cards to their original position. (It's either that or destroy them, and I'm not sure what the creator wanted.)
Barrel Roll: Select one monster on your side of the field. That monster cannot be destroyed as a result of battle this turn. In addition, if the selected monster is attacked by your opponent's monster and your opponent's monster inflicts battle damage to your life points, switch that damage to your opponent's life points.
Heart Container: Select one monster from your graveyard and special summon it to your side of the field in face-up atk or def position.
Target: The monster equipped with this card may attack your opponent's life points directly.
Poison Mushroom: This card can only be equipped to an opponent's monster. Decrease the atk and def of the monster equipped with this card by 500. Destroy this card during the end phase of your opponent's second turn after the activation of this card.
Coin Snatch: Take control of one of your opponent's monsters. Your opponent gains 1000 life points during each of his/her standby phases.
Bullet Bill: Send this card to the graveyard during your main phase. Inflict direct damage to your opponent's life points equal to the number of your standby phases that have passed since the activation of this card times 1000.
Fair Brawl: You must have at least one monster on your side of the field to activate this card. If you control one or more monsters, your opponent may not summon a monster if the number of monsters on his/her side of the field would exceed the number of monsters on your side of the field at the time of the activation of this card.
Intent to Brawl: This carrd can only be used to equip knight type monsters. INcrease the atk and def of the equipped monster by 500 points. In addition, treat the monster equipped with this card as a swift type as well. (Basically, treat the monster as swift and knight, not swift instead of knight.)
Speed Break: You may only activate this card when you or your opponent has a monster with Sonic or Shadow in its name. All monsters with Sonic or Shadow in their name gain 500 atk points and may attack twice until the end of your second end phase after this card's activation.
Chaos Control: You may activate this card when a swift monster on your side of the field is attacked. The monster cannot be destroyed during this battle phase and any life points lost during damage calculation are negated.
(C'mon gimme some SCV's for this, pleaseeeeee. I also created two cards)