Final Fantasy X has a rather unique character system that potentially allows any character in the game to learn any skill or spell in the game. Characters that are more naturally suited towards certain skills and spells are designed to learn those skills and spells more quickly, but if you play your cards right, any character can learn any skill or spell as easily, or sometimes even more easily, than the character designed to learn those abilities. All abilities are separated in four categories: white magic, black magic, skills, and special skills. Skills cost magic points to use and generally modify a basic attack in some manner. Primarily these modified attacks inflict a status ailment on the enemy, but not always. The following guide to skills in Final Fantasy X will help you decide which skills are worth getting and for which characters.
Dark Attack / Silence Attack / Sleep Attack – These three skills are normal attacks that also have a chance of applying one of three status effects on the enemy. The chance for the effect to stick is low, though rather devastating when it does, at least for the Silence Attack and Sleep Attack. Dark Attack is pretty much a waste of magic points. Wakka can learn these skills easily down his path and he probably should, but only so he can move more quickly towards Drain, Osmose, and unlocking the shortcut to Firaga.
Dark Buster / Silence Buster / Sleep Buster – These skills are nearly identical to the previous three, except the status effect has a much higher chance of actually being inflicted, the status effect only lasts one round instead of three, and the skill costs twice as many magic points to use. The last shouldn’t matter since you should only be using these skills when they are critically useful anyway, but the failure chance is a problem, as is the short duration. You desperately need Wakka to be hasted to use these skills effectively. It will take a while to learn them, but they are simply further down the path towards Osmose, so you Wakka should learn them and no other character should bother.
Delay Attack – As the name suggests, Delay Attack delays the enemy’s next turn. It is effectively like a one turn slow effect. The skill is reasonably close the starting position of Tidus, but far enough along that you are generally better off spending some time in Rikku’s skill area than moving past Haste to this skill. This is especially true since Delay Buster is basically just better in every way.
Delay Buster – The only way that Delay Buster is worse than Delay Attack is that it costs over twice as many magic points to use. Besides that, it significantly delays the turn of the enemies. There are some enemies that can only be defeated by constantly using this attack so that the enemy never acts. The best way to access this skill is by using a Level 2 Key Sphere on the locked sphere just off of Yuna’s path near Pray. This skill should be learned by every character on your team that has a good physical attack. You will generally need to teleport characters to get it, though a Skill Sphere will also work.
Power Break / Armor Break / Magic Break / Mental Break – Auron can learn Power Break for free, but the rest of the skills require modest effort to learn. Each is on his main path, so you can learn them by patience if you want to. In general, it simply isn’t necessary or worth the effort. Rather than waste your time learning these skills, it is better to have Auron teleport over to a different path and learn more useful skills or spells.
Triple Foul – This ultimate skill of Wakka’s path combines the effects of Silence Attack, Dark Attack, and Sleep Attack. This may sound useful, but you rarely need more than one of these to affect an enemy at once and the wrong one is often useless. Wakka is better exploring an alternate path, probably either the black magic or thievery path, then he is learning this skill.
Zombie Attack – Zombie Attack is a trap option. You need to travel very far down Auron’s path to get to it and it costs a Level 4 Key Sphere. This effort is not worth getting a skill that simply inflicts the zombie effect on an enemy. Basically every enemy in the game worth using this on is immune to the effect.
Mug – Mug is the upgraded version of Steal because it also damages an enemy while stealing an item. Technically this is supposed to be better, but since stealing can fail, not dealing damage is actually better, so you don’t accidentally kill the enemy. The damage isn’t modified in any way and since Rikku is the most likely character to learn this skill, it isn’t very high either. You should just skip this skill, in general.
Quick Hit – Quick Hit is a skill that lives up to its name. It deals damage like a normal attack, but the character then recovers for the next attack very quickly. It effectively puts a one round super-Haste on the character that attacks. This skill is at the very end of Tidus’ main path, so you should expect any character to learn it quickly. When Tidus does learn it, make sure to use teleports to teach it to every other character with a good physical attack as well.