Icicle

From the Super Mario Wiki

Icicles are pointy pieces of ice that have sometimes appeared in the Mario series. They first appeared in Mario Bros., as enemies that attacked by dropping from the ceiling, that first appear in Phase 16.

Icicles also appear in other Mario games, such as Super Mario 64, but have no function, and do not affect gameplay.

They also appear in an ice-cave level in Super Mario World 2: Yoshi's Island. They have the same attack as they did in Mario Bros., and whacking an egg at them would cause them to fall down from the ceiling. They would also hurt the player if they touched an icicle while it was still attached to the ceiling.