From the Super Mario Wiki
The Giant Bob-omb is an item that is used in Super Mario Strikers and Mario Strikers Charged. It is similar to the Bob-omb items, but instead of several Bob-ombs falling in a row, the Giant Bob-omb falls on one spot and explodes, hitting anyone nearby. However, it affects the user's teammates as well, so the item should be used with caution. Wario may also use this in one of his disappointment scenes in Mario Strikers Charged, in which he pulls out a Giant Bob-omb, which explodes on him.
Giant Bob-ombs also appear in Mario Sports Mix in the dodgeball game called Bob-omb Dodge, and are more dangerous than ordinary Bob-ombs. They have a wider blast range than the normal Bob-omb in this game, and cause twenty-five points of damage to the players.