Abilities in Pokemon are just as diverse as the creatures themselves. They are innate advantages a Pokemon is born with, and they can turn the tides of a battle like any move. They can damage or inflict statuses on an attacker, or they could serve as a second layer of defense for a Pokemon. Every ability has its use, but there are some 'mons that would benefit from a different one.
With some Pokemon, it would make sense if they had different abilities. Either there's a different one that would aid the Pokemon more in battle or one that would fit based on a Pokemon's PokeDex entry. Regardless, here are a few that should have different abilities than the ones they have.
8 Xatu - Forewarn
According to its Dex entry, Xatu is capable of seeing into both the past and the future. This is purely flavor text as this clairvoyance doesn't give the psychic-flying type any sort of benefit in battle, but what if it could? What if it could catch a glimpse of the future or, more specifically, a powerful move that could turn the tides of battle? The ability Forewarn does just that.
A Pokemon with this ability immediately makes note of the strongest attack in their opponent's move pool. Having a Xatu 'see' into the future and see a potentially devastating attack could turn the tides of a battle. This isn't the perfect "catch-all" counter as a Pokemon can have various alternative options to the move that was just revealed, but it can grant you an edge in battle.
7 Sneasel - Infiltrator
As a Pokemon known for stealing, Sneasel has quite a few theft-related abilities. With Keen Eye keeping it from losing sight of its target and Pickpocket allowing it to steal an opponent's item, Sneasel is very much the rogue of the Pokemon world. That being said, there's an ability that wouldn't be out of place within a Sneasel's repertoire.
The Infiltrator ability allows a Pokemon to strike a target even when they're hiding behind a Screen or Substitute. With its other abilities, it's easy to see Sneasel being able to be able to strike a target even when they're hiding behind a shield. It also fits in with the Dex entry that states that Sneasel are known for infiltrating Pokemon nests to steal eggs.
6 Gengar - Shadow Tag
Everyone knows how annoying Wobbuffet can be. Not only does it have access to Counter and Mirror Coat, but its ability, Shadow Tag, makes it near impossible to run away from. There's good reason why Wobbuffet are notorious for ending Nuzlockes. Unfortunately, or fortunately depending on who you ask, there are only a few Pokemon that get this ability, so why not add another?
Yes, Gengar's mega evolution gets this ability, but Mega's don't appear to be making a comeback any time soon so give it to normal Gengar. It's known as the Shadow Pokemon, after all, it would only make sense that Gengar would be able to keep an opponent in place using their shadow. It might seem impractical given Gengar's frailty, but it fits with the Pokemon's aesthetic.
5 Blastoise - Shell Armor
Blastoise is the undisputed tank of the Kanto region. It's incredibly bulky and can release a startling amount of force with the cannons on its shell. However, it's always these cannons that people seem to emphasize. Blastoise has other features such as the immense durability of its shell.
Quite possibly one of the bulkiest Pokemon, even after over 20 years, Blastoise is more than capable of taking big hits even from Mythical Pokemon. Because of this, it's no wonder that Blastoise sees frequent use in the competitive scene. It would be fitting for Blastoise to have access to the Shell Armor ability, which would protect it from one of its few weaknesses, critical hits.
4 Farfetch'd - Long Reach
Farfetch'd, along with Galarian Farfetch'd and Sirfetch'd, are some of the few species of Pokemon that naturally use items in battle. In Farfetch'd's case, it uses a leek much like one would a sword. However, despite striking an opponent with a weapon, it's still susceptible to abilities like Poison Point or Cursed Body.
Now, this doesn't make much sense seeing as the leek isn't part of Farfetch'd's body. To remedy this, the best option would be to give the Farfetch'd line access to the Rowlet line's Long Reach. With Long Reach, the Wild Duck Pokemon's physical moves will no longer make direct contact, giving it full use of its leek.
3 Kommo-o - Battle Armor
For a Kommo-o, their scales are as much of a part of its battle style as their actual attacks as they're used to intimidate opponents. They're also stated to be incredibly durable to the point where humans use them for weapons and armor. With such a focus being put on these scales, it would be reasonable for Kommo-o to have an ability that reflects their strength.
While an ability like Multiscale would hone in on the 'scale' aspect, it wouldn't define what these scales do for a Kommo-o. They are capable of taking multiple hits without failing, not just one like Multiscale implies. Instead, they're more like armor and sturdy enough to take continuous damage. As such the ability Battle Armor, which protects a Pokemon from critical hits, would be a more fitting ability.
2 Kecleon - Mimicry
Compared to the majority of Pokemon in the competitive scene, Kecleon's stats don't really stack up. However, its utility came from its ability Color Change, which allowed Kecleon to shift type depending on the last move that hit it. It also has the hidden ability Protean, which does the same thing but based on the move you're about to use. Both of these abilities are perfect for a chameleon-based Pokemon, but there's one more ability that it should possess.
Mimicry, the signature ability of Galarian Stunfisk, would be perfect for a Pokemon geared towards blending in with its surroundings. While it wouldn't grant the same versatility that the other two abilities grant, it would make Kecleon viable on Terrain teams.
1 Alolan Raichu - Levitate
Regardless of your opinion of the regional forms of Pokemon, you can't deny their uniqueness. With the ever-rising number of games being added to the franchise's already extensive library, it's nice to see that there's no shortage of fresh and interesting ideas. Having said that, developers definitely dropped the ball with Alolan Raichu's ability.
It's clear that they wanted to bring more attention to Terrains, but they should have used another Pokemon. Alolan Raichu's main visual appeal is that it floats on its tail and rides it like a surfboard and, while this ties into Surge Surfer, this is the perfect setup for giving Alolan Raichu the Levitate ability. This would get rid of its ground weakness and make Alolan Raichu far more viable outside a Terrain team.