Hammer Eggman (トンカチエッグマン) is the third boss of Sonic the Hedgehog 2, appearing at the end of Aquatic Ruin Zone.
When fighting Hammer Eggman, the first things noticeable are the two totem poles that rise up out of the ground with openings on the faces' mouths. Next, Eggman arrives inside another Egg Mobile, this time with a giant hammer attached to the front of it. He will stay above the two tall poles, just out of the player's reach, flying back and forth, smacking both totem poles with his massive hammer. Upon doing so, arrows will be fired out of the mouths and stick into the corresponding section of the pole across the screen. The goal here is to use the arrows as stepping stones to reach Eggman. The player may either hit Eggman directly by jumping up from the arrows, or hop onto the top of either pole and bounce off the pole onto Eggman and back, watching for his hammer (it won't crush the player, but it will make them drop their Rings). The player may also jump onto the pole while it rises from the ground at the beginning of the fight.
A total of eight hits will destroy the mech and make the totem poles sink back into the ground, allowing the player to move on to Casino Night Zone.