The storm giant, H, is the strongest giant in NetHack. As with all giants, they can throw boulders (and can start with one). True to its name, it is shock resistant, and its corpse will either give shock resistance or increase your strength.
Storm giants as pets
Giants are too large to wear shirts, cloaks, and body armor, but they will gladly pick up and wield weapons and wear other types of armor found throughout the dungeon. In addition, a pet storm giant will also ask for food or potion of healing if needed when talked to.