Corkey

 Corkey is a Badnik from Sonic the Hedgehog 3. It is found in the Launch Base Zone. It appears as an obstacle that moves back and forth on overhead tracks and ocasionally fires a laser downwards. The best way to destroy it is to jump on top of it when it's not firing

Interestingly, if one were to play as Knuckles in Sonic 3 and Knuckles, he would be uneffected by the laser if he were climbing a wall. This is because of a bug.