From Sonic Retro
Spikebonker, called Guardy (ガーディ) in the Japanese Manual, is a badnik from Sonic & Knuckles found in Death Egg Zone. The badnik hovers around the air, going left to right and occasionally turning around and going right to left, just waiting for you to come close. But close doesn't mean "too close." It just means close enough for it to shoot its spiked ball at you. And it shoots that ball quite far. But don't worry: if you're fast enough you can destroy the enemy by jumping atop its "head." Even if you miss and wind up hitting the ball (or if you miss and the ball misses), the ball comes right back.
...Oh wait, that's a reason to worry. Never mind.