The Spiny Shell's reign for Most Deadly Shell may have some competition with the Gold Shell. But before its Mario Kart debut, it served as a collectible item in Super Mario Galaxy and Coin producer in New Super Mario Bros. 2.
In Mario Kart Arcade GP DX, this luxurious and highly dangerous Koopa shell locks onto players and rocks them with a deadly explosion. Because of the Gold Shell's impact on enemies, it's more of a rarer Item.
You might be wondering what is worse than a Red Shell or a Black Shell. What about the two of them combined? Like the classic red-colored Item, the Gold Shell is able to track down an opponent in front of the users kart. This way, it's very hard to miss the intended target. Once the projectile reaches the enemy racer, instead of just hitting them with normal damage, it explodes harshly (characteristic of the Black Shell). That way, a packed in group of racers can be taken out with a single blow (literally a blow).
Using a Gold Shell as shield protection isn't really considered "protection". It will simply blow up behind you. So, like a Bob-omb, it's best to shoot the gilded Koopa shell back just before the enemy Item lands a hit so that the detonation is a safe distance away.
The Area Of Effect damage dealt by Gold Shells prevents any on-vehicle shields, meaning that holding a Banana or brandishing Triple Green Shells will help nothing. Your only chance is to hit it while it's coming at you with one of YOUR OWN Items. And that's very difficult, so be prepared to explode. You can at least delay it with a Mushroom, though...
- Really, the only differences between a Spiny Shell and Gold Shell is that the former flies around in some of the Mario Kart games. In the rest, the Spiny Shell rolls across the ground, bowling over anyone and exploding on impact. Also, the Gold Shell will not target first place, but it's manner of destroying opponents is the same.
- Oh, and another difference is that one is blue and one is yellow.