From WiKirby, your independent source of Kirby knowledge.
Gigatzo is an invincible enemy that first appeared in Kirby's Return to Dream Land. It stays in one place and shoots large flaming projectiles in a straight line that cannot be inhaled or reflected.
Gigatzo is practically a large version of Shotzo. In its debut in Return to Dream Land, it was characterized with a big red barrel and giant flaming projectiles, though it fired infrequently and could not re-aim itself, similar to its relatives which also debuted in that game, Volttzo and Coldtzo. Unlike the other large cannons, however, Gigatzo is shown to be capable of affecting certain platforms it is situated on. In one of the alternate dimension sections in Dangerous Dinner, it is shown to cause pillars it is situated in to react to its recoil and move downward, creating a crushing hazard for Kirby.
Gigatzo returns in Kirby: Triple Deluxe, though it is not quite as large in most cases. However, now it is capable of re-aiming itself in certain instances. It appears again in Kirby: Planet Robobot, essentially unchanged from its Triple Deluxe incarnation.