Sub weapon

"Divert the enemy with weapons like Splat Bombs or the Sprinkler. Pro tip: You can try out the weapons at Ammo Knights before you buy."

- Splatoon's official website

The Sub Weapon is a secondary weapon in Splatoon and Splatoon 2. They use up considerably more ink than a Main Weapon, and as such, usually serve specialized purposes limited to specific combat situations and are not often used as a main method of inking the environment. When there's a sufficient amount of ink to use the Sub Weapon, there is a sound effect and the light on the back of the player's ink gauge will light up.

The Ink Saver (Sub) ability will reduce the amount of ink consumed by a player's Sub Weapon. The Bomb Range Up ability allows bombs, Point Sensors, and Disruptors to travel farther when thrown. The Damage Up ability will increase the damage of bombs and Seeker.

Splat Bomb
This is a pyramidal grenade that can be thrown normally. It explodes after 2-3 seconds, splatting enemies nearby and inking a small area around it.

Burst Bomb
This is a water balloon-shaped bomb that can be thrown normally. It explodes immediately upon contact and can splat enemies in 2-3 hits. These consume a small amount of ink for a sub weapon and can be thrown rapidly.

Suction Bomb
This is a bomb with a suction cup that can be thrown normally. It sticks to the first surface it touches and explodes after 2-3 seconds.

Point Sensor
This is a device that can be thrown normally. When hit by it, your opponents are effectively echolocated, and can be seen by your team for a short time.

Disruptor
This is a potion that can be thrown normally. When hit by it, your opponents' run and swim speeds, as well as their ink recovery rate go down, making them easier to splat.

Splash Wall
This is a T-like structure that can be thrown a small distance. Once it activates itself, it showers your color ink, blocking enemy movement and fire.

Sprinkler
This is a sprinkler that can be thrown normally, and sprays your color ink in a circle until it is destroyed or another one is placed.

Seeker
This is a device that gets placed at your feet. It runs forward and follows any opponents it sees, after a short time, or it hits something, it explodes and splats the enemy it hit, if applicable.

Ink Mine
This is a bomb that can be placed at your feet. It cannot be seen by your opponents, and it explodes if they walk too close to it.

Squid Beakon
This is a device that can be placed at your feet. It appears on everyone's Wii U GamePad map, and one teammate can Super Jump to it.

Splatoon 2
In Splatoon 2, every sub weapon returns except the Seeker and the Disruptor. They act mostly the same as in the original game.

Curling Bomb
This is a bomb that can be placed at your feet. It moves in a straight line and bounces off walls, inking the ground until it explodes. You can adjust the time until detonation by holding down until it is thrown.

Autobomb
This is a bomb that can be thrown normally. It acts greatly like a Seeker, as when it lands, it starts to home in onto the nearest opponent until it explodes.

Toxic Mist
This is an object that can be thrown normally. It creates a mist that when opponents are caught in it, they move slower and their ink is slightly reduced.

Tips

 * If you notice a red glow in your Ink Tank, the glow will only disappear if there isn't enough Ink in the Ink Tank to use for the sub weapon. The Red glow is always there at a start or a Regular Battle, Ranked Battle, and in Octo Valley during exploring areas and missions.

List of Sub Weapon sets
 List of Sub Weapons sets in Splatoon