The Egg Walker is a mecha used by Dr. Eggman in Sonic Adventure 2. He created it to infiltrate Prison Island and awaken Shadow the Hedgehog. It becomes his main battle vehicle in the rest of the game. It is actually the Eggmobile with legs and weapons equipped.
It is armed with a Volkan Cannon that can shoot regular ammo, a missile launcher, lock-on capabilities, and punching glove. Upon finding certain items, the standard Volkan Cannon becomes a Bazooka, capable of destroying steel crates, the standard lock-on missile becomes a Laser Blaster, capable of "splash damage," and a Jet Booster, giving it the ability to hover in mid-air. In 2-Player Mode and the second battle for Tails, it's also equipped with a rocket launcher and a laser cannon.
After presumably killing Sonic, Tails attacks Eggman and he fights him in an attempt to take his Yellow Chaos Emerald. In the end, both vechicles were destroyed. However, Eggman snuck away with the Chaos Emerald, implanting it in the Eclipse Cannon.
Eggman later recreated it as multiple robots he deployed in Soleanna in the events of Sonic the Hedgheog. It's an advanced model of the Egg Cannon, though they lack flying abilities. The Egg Walker is equipped with twin laser cannons that fire energy beams in a straight line.