Hero

Hero commonly refers to Agent 3, Agent 4, Agent 8, or the new Agent 3, the protagonists of the single-player modes Octo Valley, Octo Canyon, Octo Expansion, and Return of the Mammalians, respectively. It may also refer to the single-player modes themselves, also known as Hero Mode. Other things it may refer to are:

The suits worn by the New Squidbeak Splatoon:
 * Hero Suit
 * Armor

The replica gear based off of these suits:

The main weapons used in Octo Valley and Octo Canyon:
 * Hero Shot
 * Hero Charger
 * Hero Roller
 * Hero Blaster
 * Herobrush
 * Hero Slosher
 * Hero Splatling
 * Hero Dualies
 * Hero Brella

The replica main weapons based on them:

The Splatfest:
 * Hero vs. Villain