Kuribo is one of my favorite cards. It's a fairly simple card, and there's honestly not much to discuss. However, American players seem to be shying away from this card, and that makes me very confused. I see people playing Dian Keto, but not playing Kuribo...
I guess the first thing would be to clarify exactly how the fuzzball works. If an opponent's monster attacks you directly, you can prevent all of the damage that it deals to you. If a monster attacks a monster of yours in attack position, any extra damage that would go through to your Life Points is prevented. Your monster will still recieve damage; unlike Messenger of Peace, Kuribo does nothing for your monsters.
This being said, why would a person play Kuribo over Messenger of Peace? After all, Kuribo only prevents damage to you from one source, while Messenger of Peace prevents all damage from all sources for the entire turn.
Well, the reason is simple. Kuribo is one of the only, if not the only, card that violates an essential rule of the game. Kuribo is perhaps the only card in the entire game that can be played from your hand on your opponent's turn. But is this really that good? Yes, it is.
If you have Traps on the field, you opponent will usually make his or her moves cautiously. However, without Traps, they will probably become more aggressive, often leaving themselves open in the process. A common example of this is when your opponent believes that they can kill you on that turn. When you play Kuribo, ruining their evil plans, the ball is back in your court, and you'll have a heavy advantage.
Even if Kuribo is expected, that means that your opponent will always act cautiously if you have even one card in your hand. It doesn't take an expert to know that scaring your opponent gives you an advantage.
That's not all, of course. Kuribo has his very own combo card. Multiply is a promotional Quick-Play Magic that allows you to sacrifice one of your face-up Kuribos in play to fill all of your empty Monster Zone Slots with Kuribo tokens in defense position. Kuribo tokens are exact copies of Kuribo, except without the ability. However, you aren't allowed to sacrifice the Kuribo tokens to summon monsters. You can, however, sacrifice them for other things, like a Cannon Soldier, a Deck Destruction Virus of Death, or a Magic Removal Viral Cannon.
Additionally, as is mentioned above, little Kuribo is a small, Dark-affinity monster, which means that he can be sacrificed for the Deck Destruction Virus of Death. Even better than that is the fact that a Black Forest Witch or Critter can search your deck for Kuribo when they die.
Of course, the main reason to use Kuribo in almost any deck is the deadly Devil Franken deck. Because Devil Franken's strategy revolves around clearing the field of Traps, then Monsters, it will feel fairly sure that it has won when you have no cards in play. Dropping a Kuribo from your hand will not only keep you alive, but leave you in a position to devestate your opponent.
Don't mess with the fuzzball! ^_^
