Kaboomba

The Kaboomba is a walking cannon enemy that first appears in Super Mario World 2: Yoshi's Island, though it originated in prototype versions of Super Mario World.

Super Mario World 2: Yoshi's Island
Kaboombas only appear in The Cave Of The Mystery Maze and Raphael The Raven's Castle. They attack by shooting heavy cannonballs that fall to the ground and explode after a few seconds. Yoshi can safely stand on them, and eating them does nothing. An egg or Ground Pound disposes of them.

Yoshi's Island: Super Mario Advance 3
Kaboombas retain their role in the Game Boy Advance port, Yoshi's Island: Super Mario Advance 3.

Yoshi's New Island
Kaboombas make a return appearance in Yoshi's New Island.

Super Princess Peach
Kaboombas also appear in Super Princess Peach, where they are named Cannons. The Calm Cannon, a sleeping variety, also appeared.

Trivia

 * The Nintendo Player's Guide description for the Kaboomba is erroneously accompanied by an image of one of the cannonballs instead of the enemy itself.