The Splat Brella is a Hero Mode/Dlc weapon introduced in Splatoon 2. You get this weapon in World 4's Mission 20.
The Splat Brella is a weapon type that's use resembles a Shotgun. The weapon is outfitted with a wide projectile spread but is limited to close-ranged effectiveness. The player can open the umbrella to shield themselves from attacks coming directly in front of them. If the player holds the umbrella open for over two seconds the umbrella separates from the weapon itself and flies foward, becoming a traveling shield the player can utilize to break through enemy defenses.
There is a cooldown after the player launches the umbrella before the player can use it again.