Yu-Gi-Oh! World Championship Tournament 2004

If you attack and destroy a Slate Warrior with a Fiend type monster on your side of the field when you have a Dark Ruler Ha Des face up on your side of the field, the slate warrior will still weaken your monster, even though the effect of Dark Ruler Ha Des should prevent that from happening.

Have Solemn Wishes active on your side of the field and then filp summon Fiber Jar activating its ability, when you go to draw your cards although Solemn Wishes isn't on the field you still gain 2500 life points!

The Graverobber card states that you can take a spell card from your opponent's graveyard and it will only work if you activate the spell card you took during your turn, but you have to pay 2000 life points to activate it.

You can play the card you took without paying the 2000 life points by first placing it on the field and then activating it while its on the field. The game somehow forgets the card is in play because of Graverobber and normally plays out the card. You will however end up paying the 2000 life points if you play the card you took while its in your hand, so make sure you place the spell card on the field first before you play it so to avoid the 2000 life point penalty

Thunder Nyan Nyan is a powerful 1900 ATK Light element monster that is immediately destroyed if you have a non-Light element monster face-up on your side of the field. However, if you use Snatch Steal to take a monster from your opponent, it doesn't count as a monster on your side of the field, and therefore Nyan lives. This doesn't work with Change of Heart.