Splatoon/Sub-weapons and specials

Other than your primary weapon, you also have access to a sub-weapon, which uses up a lot of ink but usually has a significant effect, as well as a special, powerful tools that can only be used after inking enough turf. The sub-weapon and special you get is always tied to your main weapon, so even weapons that share the same stats can require different playstyles depending on the sub-weapon they have.

Sub-weapons
Sub-weapons mostly consist of powerful thrown grenades or helpful support items. They typically use up a lot of ink, so they can't be spammed carelessly. The ink pack on your back will glow whenever you have enough ink to use your sub-weapon, serving as a useful visual indicator.

Splat Bomb
Splat Bombs behave like standard grenades: they explode a while after being thrown to deal heavy damage and spread ink in its blast radius. The bomb has a short fuse which only counts down when the Splat Bomb touches a solid surface like a wall or floor. Splat Bombs are versatile and can be used to cover areas outside your reach, such as enemies beyond your main weapon's range or around corners. They are also good for map control by forcing foes out of strategic positions. You can control when the bomb explodes based on the way you throw it. For example, rolling a Splat Bomb along the ground or off the ledge activates its fuse earlier, causing it to explode faster than a tossed Splat Bomb at the cost of range.
 * Ink cost: 80%
 * Damage: 180 (decreases with distance from the center of blast)

Burst Bomb
Burst Bombs deal a fraction of a Splat Bomb's damage for a fraction of the ink required. Since it uses up so little ink, it is very spammable and is often used more like an alternate main weapon than a backup. Burst Bombs explode immediately, which limits their use to direct combat, although they can also be used to quickly cover a patch of turf for weapons that can't do so. Burst Bombs kill in 2 direct hits or 3 indirect hits, so you can take on foes in mid-close range engagements exclusively using Burst Bombs. Burst Bombs are usually utilized to make up for a main weapon's weaknesses. On short ranged weapons like the Carbon Roller, it's used to attack foes that are out-of-reach; on long-ranged weapons like the E-liter 3K, they are close-range defenses against flanking or surprise attacks.
 * Ink cost: 25%
 * Damage: 60 (Direct impact, lower damage if hit with splash)

Suction Bomb
Suction Bombs have suction cups that attach to any floor, wall or ceiling they touch. They have the same damage and blast radius as Splat Bombs but a slightly longer fuse. Suction Bombs have the similar uses to the Splat Bomb, only with improved ability to deal area pressure. Since they take longer to explode, they also scare foes away longer, letting you restrict their movement more effectively. Conversely, it is also harder to splat enemies as they have more time to react and escape before the bomb blows up. Fortunately, being able to stick Suction Bombs lets you use it more unpredictably, such as by attaching a Suction Bomb on the wall around the corner to catch foes rounding the bend.
 * Ink cost: 70%
 * Damage: 180 (decreases with distance from the center of blast)

Seeker
Seekers are small boats that slowly travel forward, leaving a trail of ink behind. They can move up ramps, and will explode upon hitting a wall or enemy. Seekers has minor homing capabilities against enemies, but they cannot detect any foes hiding in their ink. Seekers move slowly and can be avoided by entering squid form or simply jumping over them, but their ink trail and interaction with terrain make them interesting explosives. Seekers can carve ink paths through neutral or enemy territory, helping you hurry to your objective or approach a targeted enemy. They are most effective on long, straight corridors as they can move their max distance uninterrupted and cover the corridor efficiently. You can use a Seeker's behavior to your advantage, such as by sending them off ledges or up ramps to surprise enemies.
 * Ink cost: 80%
 * Damage: 180 (decreases with distance from the center of blast)

Ink Mine
Ink Mines cannot be thrown, only set on the ground near you. Once set, the Ink Mine will activate and explode if an enemy gets close, the surrounding area is covered by enemy ink, or after a certain amount of time has passed. You cannot place another mine until the previous mine explodes. Ink Mines are Suction Bombs taken to the extreme. They are really good at stage control, being able to lie dormant for roughly 10 seconds and driving off foes that set them off, but they are utterly ineffective at splatting enemies. The mine glows brightly for a moment before exploding, giving a small window for foes to react to it, so good Ink Mine placement is necessary to make them a considerable threat. Small, actively contested spaces are the best candidates, with the most common being the tower in Tower Control.
 * Ink cost: 60%
 * Damage: 180 (decreases with distance from the center of blast)

Disruptor
Disruptors are thrown like Burst Bombs, but instead of dealing damage, they coat all foes caught in the blast radius with a debuffing liquid. Foes under the effects of a Disruptor debuff experience drastically reduced walk speed, swim speed, jump height, ink recovery and become visible to enemies even when swimming in their own ink. Even though it doesn't directly hurt opponents, the Disruptor is a powerful support tool that cripples the fighting abilities of enemies, ruining their mobility and making them easy prey for the user and teammates. Their relatively cheap ink cost lets you spam it somewhat, which is useful for scouting out areas or pressuring foes.
 * Ink cost: 50%

Point Sensor
Point Sensors function similarly to Disruptors, but instead of debuffs, they mark the position of enemies within the blast for all teammates to see. The Point Sensor is a smaller-scale version of the more commonly seen Echolocator special. While its effects are minor compared to other thrown sub-weapons, it can be very helpful if you mark the right enemy. The Point Sensor has a low ink cost, so you can fling several into enemy territory to detect any potential ambushes. Generally, you can ignore long-range attackers like Chargers that can shrug off the effects by keeping themselves safe through sheer distance. Instead, go for mobile or stealthy flankers like Splash-o-matics or Rollers as they rely heavily on the element of surprise to get kills.
 * Ink cost: 40%

Sprinkler
Sprinklers can be attached to any solid surface, after which they will start spreading ink indefinitely, two drops at a time while slowly rotating. Only one Sprinkler can be on the map for each player, using another one causes the previous to disappear. The Sprinkler is purely a support tool used to both claim turf and harass enemies. They can ink a surprisingly large area given enough time, and leaving a Sprinkler to ink up your base can net you a big chunk of your special meter. Sprinklers have about the same health as players, so they serve as moderately effective distractions in enemy territory, although it uses too much ink for direct combat. The best Sprinkler placements can ink contested spots while being hard to destroy. Typically, these positions are angled on walls, behind corners and sometimes even on low ceilings.
 * Ink cost: 80%
 * Damage: 30 per drop

Splash Wall
Splash Walls are thrown a short distance ahead before activating, creating a temporary ink barrier that blocks all of your shots, but allows your own shots to pass through. Enemies that pass through the wall are instantly splatted, but they can attack the Splash Wall to reduce its duration, and there can only be one Splash Wall per player active at any given time. Splash Walls are commonly given to long-range weapons like the .96 Gal and Splatling, their purpose being an additional line of defense. Splash Walls block all shots from one direction, letting you fire at foes with impunity. Splash Walls can also be placed to your sides to ward off enemy flanks while you focus on another direction.
 * Ink cost: 60%

Squid Beakon
Placing a Squid Beakon creates a super jump spot that can be used only once. Up to three Squid Beakons can be placed on the map per player, each of them visible to both teammates and enemies. Squid Beakons are purely supportive items, and how useful they are depends on the locations they're placed in. Since you can already super jump to any living teammates and the spawn point, it is best to leave them in hidden, low traffic areas with quick access to the frontlines. Since enemies can see the position of Squid Beakons on the minimap, you really need to hide them well. Squid Beakons are very helpful for difficult sieges or pushes, transporting fallen teammates to the battlefield quickly even in the event of a major loss. They can also sometimes serve as distractions since enemies would want to get rid of them quickly, setting them up for an ambush.
 * Ink cost: 80%

Specials
On the top-right corner of the screen is your special bar. It will slowly fill up when you ink turf, and lets you unleash a powerful special when it is fully charged. You will briefly shine and your Inkling's hair will start flaming once you get your special, visual cues visible to both friend and foe. Using a special instantly refills your ink tank. Dying will take a large chunk off of your special bar, so make sure to survive when you have a special until the right moment to use it.

Inkstrike
The Inkstrike is a ballistic ink missile that can target anywhere on the map by tapping on the desired location on the Gamepad minimap. Shortly after it is launched, an indicator will appear followed by a deluge of ink that coats the area. Enemies inside the strike radius will be splatted, but it is possible to survival getting hit by staying at the edges of the attack. The Inkstrike is a fairly common special primarily used to claim turf. Since it has infinite target range, you can ink turf deep within enemy territory without being anywhere near it. Most notoriously, it is often launched at the very end of a Turf Wars match to get extra turf without enemies being able to retaliate. It can also be used to drive enemies out of contested areas such as a Splat Zone. However, you are helpless after activating the special before it is launched, so find a safe spot to hide in before using it.
 * Turf required: 180p

Inkzooka
Activating the Inkzooka replaces your primary weapon with a powerful ink launcher that fires swirling columns which instantly splats foes. The ink tornadoes travel very quickly, leave long trails of ink behind and have extremely long range comparable to an E-liter 3K. They're also tall projectiles and can continue past some walls and ledges, so they are excellent at targeting Charger perches, one of the primary uses for this special. The general purpose of the Inkzooka is to get as many kills as you can and force your enemies on to the defensive with its sheer power. Beware of flanks while you're using it, since the slow fire rate and narrow paths of the ink pillars make it difficult to defend yourself at close range.
 * Turf required: 220p

Killer Wail
The Killer Wail creates a huge, long, and cylindrical soundwave that instantly disintegrates any enemy players within it. It is quite slow to take out and use, during which you are entirely vulnerable to enemies, but you can aim and target it like a normal weapon to determine the direction of the Killer Wail. The Killer Wail doesn't spread ink, but it's pretty poor at killing as well most of the time by giving foes an obvious warning before it fires. The function it truly excels at is area denial. Since staying inside the soundwave is an instant kill, it forces enemies to either avoid the wail during the warning or die trying. It also deals continuous knockback to Bubbler and Kraken users, preventing them from accomplising much. When aimed at an important area or objective, it lets your teammates close in and retake the area or objective in question. Another benefit of the Killer Wail is that it is very cheap, giving you many chances to use it over the course of the match.
 * Turf required: 160p

Bomb Rush
Bomb Rush lets you throw as many sub-weapons as you wish for its duration without consuming any ink. The version of Bomb Rush each weapon has depends solely on its sub-weapon. The Burst Bomb Rush is by far the weakest. It can surely cover a lot of turf really quickly, but doesn't threaten enemies unless you're directly targeting players with the Burst Bombs. Splat Bomb Rush is both unpredictable and hard to avoid due to the ricocheting nature and low fuse of Splat Bombs. It does a good job of scaring foes away, letting you claim enemy turf with ease. The Suction Bomb Rush is by far the most feared, as they can be arranged like an organized minefield, turning a section of the map into no-man's-land. It is also very difficult to challenge, as you may find yourself trapped by the sheer amount of Suction Bombs going off at once.
 * Turf required: 180p

Kraken
The Kraken temporarily turns you into a huge, invincible squid that instantly splats nearby foes by jumping. The Kraken functions just like normal squid mode; you swim a bit slower but can still climb walls, and you leave an ink trail as a nice bonus. The Kraken is an intimidating special, as using it will often cause foes to flee. It's main purpose is to splat foes and it lets you pursue enemies relentlessly to get the kill. It also makes you completely invulnerable to attacks, but you will take knockback when hit. A calm opponent with the right weapon can keep you at bay simply by firing at you, potentially wasting your special. Also worth noting is that the Kraken still drops through grates like normal squids, so don't get too overzealous when chasing foes across dangerous terrain.
 * Turf required: 180p

Bubbler
The Bubbler briefly creates a bubble shield that renders you completely invulnerable, but lets you retain all normal abilities. Even though the invincibility lasts shorter than the Kraken, the Bubbler has a major perk in that you can share the shield with allies by bumping into them. This trait makes the Bubbler the ultimate support special, able to easily turn the tide of a teamwide skirmish or facilitate a dangerous push. With the shield, you can attack enemies and push forward with impunity. The Bubbler does have an exploitable weakness in that enemy attacks cause increased knockback, so players with greater range can keep you from advancing, but is otherwise nearly uncounterable.
 * Turf required: 180p

Echolocator
The Echolocator reveals the location of all enemy players on the map. This special has an extremely powerful effect that barely requires effort from your part to use. Knowledge is power, especially when stealth and area control is so important in this game. Using the Echolocator effectively denies the enemy from using sneak attacks and lets you observe their battle formations, letting your team work around and take out foes. The Echolocator is useful just about any time during a match, except when a teammates is using their Echolocator, so you can even use it for a quick ink refill. However, it is best used in conjunction with other specials like the Inkzooka or Killer Wail, letting your team know exactly where to aim to hit the hardest.
 * Turf required: 200p