Spiker

Spiker (called ShinShin in the Japanese manual), located in Hill Top Zone, are little red insects with a large spike on its head. Sometimes they are found walking on the ground and fire the spike upwards when you jump over them, or on the ceiling and fire the spike when you pass under them. Once they lose the spike, though, they're almost harmless. Just spin attack to finish the job off.

The Sonic 3 enemy Turbo Spiker is evidently an improved model of this Spiker; it moves faster and fires its spike at a slight angle, but its behavior is otherwise identical.