Giant Blue Shell
From the Super Mario Wiki
Giant Blue Shells are a rare variety of Koopa shells.
In the Mario Strikers series, the Giant Blue Shells are items that can be collected by the players. When fired, it will shoot at the opposing team, freezing them when it hits them. However, unlike a normal Blue Shell, the Giant Blue Shell rolls over a player and keeps on going. This allows it to freeze other players, both the foe's team and the player's team. Another difference is that the giant versions only come individually, whereas the normal shells tend come in groups of three.