Spiny Shell

A Blue Item is an item featured in multiple Mario games that has varying abilities depending on the video game. In the orignal title (Super Mario World for the SNES), its only distinct purpose was giving any Yoshi the ability to fly for a short time when eaten.

In the Mario Kart series, Blue Shells are arguably one of the more prefered items. Rather than being just regular Koopa Shells colored blue, they feature spikes and, more recently, have wings as well. When thrown, it'll head towards the racer in first place and attack them. In the earlier titles, the Blue Shell would not only attack the person in first place, but would also plow through any enemies in front of the racer who threw it.

In Super Mario Strikers and its sequel Mario Strikers Charged, Blue Shells would freeze oppoents on impact, though they would not home in on them as Red Shells are capable of doing.

Blue Shells also appeared in New Super Mario Bros. where they could actually be worn by Mario or Luigi. They weren't as helpful as some of the other items, though they were fun to use. They would also allow you to travel faster than before and ram into enemies just as a kicked shell would do.