Game Freak introduced Abilities into Pokémon during Gen 3, and they were literally game-changers. Having the right Ability makes all the difference with your Pokémon. Some abilities can drastically improve effectiveness, while others are essentially useless (or even detrimental). Knowing which Abilities are of most benefit and which ones you should avoid, can save you from picking a party member that will never be able to pull its weight.
It's time to take a look into the best and the worst Abilities. Keep in mind, the list intentionally excludes those Abilities that are strictly for handicapping a super-powerful Pokémon (Truant, Slow Start, and Defeatist), since they are intentional disabilities. That said, here are 5 fantastic Pokémon Abilities and 5 that aren't worth your time.
10 Fantastic: Weather Setting Abilities
Weather is a massively potent field effect, so automatically taking control of it with Drought, Drizzle, Sand Stream, or Snow Warning is extremely useful. While these Abilities are rare, the effects of their respective weather changes cannot be discounted. Deal more damage with Fire and Water-type moves thanks to Sun or Rain, let your Rock-types gain a Special Defense boost in Sandstorm, or enjoy the perfect accuracy that Blizzard gains in Hail. There's a reason why weather setting Pokémon are a favorite with competitive players!
9 Worthless: Stall
The Stall Ability is an interesting case. Any Pokémon with Stall will always move last, regardless of Speed stats. While this seems like just another intentional handicap for an otherwise over-powered creature, in reality the only Pokémon "gifted" with Stall is Sableye. With a default Speed stat of 50, Sableye is certainly not fast, and almost always moves last anyway. The rest of its stats aren't noteworthy either. So, the need for such a big handicap in such an average Pokémon is a complete mystery.
8 Fantastic: Prankster
Fitting with its name, Prankster is a sneaky Ability causing any non-damaging moves to have 1 point added to its priority. Translation; you can almost always get your Stat Moves in first. This is especially useful for Pokémon that are naturally slow, as it allows them to act before even the fastest of opponents. Give your foe a status condition before they can move, boost your stats before they can stop you, or set up Moves like Reflect or Light Screen to bolster your defenses before the opposition gets an opportunity to attack. The utility Prankster gives you is phenomenal, and its only real drawback is that Dark-types are immune to its effect.
7 Worthless: Illuminate
The Illuminate Ability increases the encounter rate of wild Pokémon by 100%, making them show up twice as often. Wild Pokemon encounters are already super common, no matter which game in the series you are playing. Having more of them really doesn't benefit you in the slightest, and becomes increasingly annoying as you progress through the game.
The amount of additional time all of these extra encounters add up to is ridiculous, and wasted. The closest thing to any sort of use Illuminate could serve is helping with the completion of the Pokédex (more encounters equals more chances to Catch Them All,) but nothing really calls for this drastic increase in encounter rate. It's unnecessary overkill.
6 Fantastic: Intimidate
Intimidate is another Ability with excellent utility. Its effect is simple, your opponent's Attack stat decreases by 50% until they use up a turn to switch out the Pokémon in play, or use a stat move to raise their Attack. This is can be quite the surprise for unsuspecting opponents, who find themselves at an immediate disadvantage. The lowered Attack stat allows your Pokémon to take physical hits they otherwise could not, giving you more rounds to strike back. Combine Intimidate with Moves that lower Special Attack or increase your own Special Defense, and you have made yourself a defensively capable team.
5 Worthless: Run Away
The sheer fact that the Run Away Ability even exists is honestly sad. It gives the user the Ability to always run from a wild Pokémon battle with no chances of failure. Already this is questionable, because successfully escaping wild Pokémon is not that difficult. Have a Pokémon that is faster than the wild one your fighting? Congratulations, it will probably be a successful flee attempt. What makes this all the more hilarious, is the fact that there is not just one, but two items (the Smoke Ball and the Poké Doll) that give you the same effect as Run Away. In short, Run Away is a complete waste of an ability slot. There is no reason to ever carry it.
4 Fantastic: Solid Rock
This Ability is a great concept. Solid Rock takes the damage of Super Effective moves and decreases it by 1/4. While this may not sound incredible, this reduction of Super Effectiveness is actually quite formidable. Take Camerupt and Rhyperior as examples. They usually go down like chumps to strong Water attacks (due to it being their quadruple weakness,) without giving them any real chance to fight back. Solid Rock helps them to survive Super Effective hits they otherwise would not. This gives them the opportunity to possibly KO said Water user or use stat boosting Moves to make the rest of the battle go smoother. The bottom line; Solid Rock increases their usefulness to your team, and that's what you're always shooting for.
3 Worthless: Anticipation
Anticipation makes the user "shudder" (with a handy text box stating exactly that) if the opponent has a Move that is Super Effective against your Pokémon within its move set. While you might think this could have some usage in gaining decent information on what your opponent has in store for you, any player with basic knowledge of the moves Pokémon tend to carry completely nullifies this Ability's advantage.
Say your Fighting-type is up against a Psychic-type and the Anticipation Ability activates, you now know they have a move you're weak to. Except of course, you already knew Fighting is weak to Psychic. Of course, the Psychic-type has a Psychic move. The surprise would be if it didn't!
2 Fantastic: Clear Body
Let's face it, anything that gives you some form of immunity, is a good thing. The Clear Body Ability gives a Pokémon Immunity to any stat reductions brought on by their opponent, regardless of whether said reductions are caused by other Abilities or Moves. This is amazing for blocking Intimidate or Moves that cut stats in half, like Acid Spray for Special Defense. In the hands of a clever player, who knows how to predict their foe, this Ability can give them a mass of extra utility. Know your opponent is about to switch over to an Intimidate user or going to use a stat lowering Move? Send in the Clear Body user. Your opponent will immediately discover that they have just wasted their time.
1 Worthless: Klutz
This could likely be considered the biggest waste of an Ability slot of all time. Klutz makes it so the user cannot glean the effects of its Held Item. Both Held Items and Abilities are incredibly important to making competent Pokemon teams. So, the fact that Klutz uses up both the Ability and Held Item at once is actually astonishing. The best thing to do with Klutz is to find a way to force it onto your opponent, with a Move like Skill Swap. You will have taken away both their Item and Ability on the same turn (which is an admittedly powerful effect,) but otherwise, Klutz is not only not worth the bother, it's something to be avoided at all cost.