When trainers get their first Pokémon starter, they'll usually have an offensive move and a status move. Status moves are any moves that alter the other Pokémon (or their own!) and usually don't cause physical damage. Some moves can be a combination of both.
When picking a complete moveset for each Pokémon on their team, trainers are quick to forget status moves — and often, rightly so. Many status moves just don't provide the advantages that a physical or special move might, and are quicker to go than something with higher attack power.
Some, however, are shockingly worth keeping!
10 Worth Learning: Disable
The move Disable is a Psychic-type move that can be really useful when facing a powerful opponent. If you're going up against a particularly powerful trainer or gym leader and they have that one move that utterly decimates your Pokémon, send out a Psychic-type with Disable. For a certain amount of turns, the move used by the other Pokémon will be unavailable to them.
9 Not Worth It: Magnetic Flux
Allies who have the Plus or Minis ability are lucky enough to have their Defense and Special Defense stats raised by this move, but in reality, it's not worth it. It's not practical for this to take up a move slot when better ones are available. It can only affect a limited amount of Pokémon and there are plenty of other moves that can raise Defense far more efficiently — and not exclude the user themselves from the effects.
8 Worth It: Embargo
Embargo is a Dark-type move that prevents the other Pokémon from using any held items. This might seem a little useless, since held items don't do a lot of good, but there's another advantage — it prevents the use of items from the bag on this Pokémon.
This is a game-changer if you're up against a trainer who keeps using a Full Restore at the very last second, bringing that Pokémon with whittled down HP back to full health.
7 Not Worth It: Growl
Growl is one of the moves that starter Pokémon usually know, and it's quickly deleted... for good reason. Growl lowers the Attack of the opposing Pokémon, but it's not enough for it to have any real effect on the outcome of the battle. The battle would truly need to be coming down to the wire in a very specific set of circumstances for Growl to be worth having, and rarely will experienced trainers use this.
6 Worth It: Minimize
Minimize raises the evasiveness of the Pokémon, which may not seem like much — but use it a few times in a row and watch your opponent become extremely frustrated as all of their attacks miss. If their moves have low accuracy as it is, then the chances of them hitting you will be minimal — and as high power attacks often do have low accuracy, this is a perfect move for battles later in the games when the stakes are higher.
5 Not Worth It: Tail Whip
Tail Whip is the cousin of Growl; the status move that starter Pokémon are taught that simply isn't worth knowing. It lowers the Defense of the opposing Pokémon but really, don't bother using this at all. In any battle when your starter is that new, it's better to just keep ploughing ahead with the offensive attacks.
4 Worth It: Sleep Powder/Poison Powder/etc.
Bug and Grass-type Pokémon tend to know moves like Stun Spore, Sleep Powder, Poison Powder, etc. Each of these moves has a different effect, but the opposing Pokémon will suffer for it. They'll either be paralyzed and might not be able to attack, fall asleep and be rendered useless for a few turns, or suffer damage from poison, and that's all worth it.
3 Not Worth It: Mud Sport
Mud Sport lowers the power of Electric-type moves and it's too specific to justify keeping around.
When you only have four slots for moves, one that only lowers the Attack stat of one type is a little useless. If you want a status move, it's better to have one that just generally lowers the Attack of the opposing Pokémon — preferably sharply.
2 Worth It: Electric Terrain
Electric Terrain, however, is probably worth it in certain situations. Not only does it increase the power of Electric-type moves, it means that no Pokémon on the battlefield can fall asleep. If you're up against a Butterfree that keeps getting you with Sleep Powder, or a Hypno that keeps getting you with a Psychic-type attack, it's time to render them ineffective.
1 Not Worth It: Splash
Poor Magikarp. When you catch one, chances are that the only move it'll know is Splash. It's considered a status move, but it should really be considered a 'nothing' move, because that's exactly what it does. Magikarps are notoriously hard to train in games that don't have automatic exp share, because how exactly are they supposed to fight?
Still, the evolution makes it all worth it. Go, Gyrados!