Field Effects
From Gen III to Gen VIII, if you put a Pokemon with this ability first in your party, you have a 50% chance to force an encounter with a Pokemon sharing the type of all of the Pokemon with this ability
Static
From Gen V onwards, if a Pokémon has an effective speed greater than 1809, it will ignore the effects of this move.
Trick Room
This Pokemon's evolution has a niche in RBY OU for its ability to learn Surf through an 1997 event, but a few months later an event saw this Pokemon being able to also learn Fly.
Pikachu
In 2014, Verlisify posted a video featuring a set for this Pokemon. This Pokemon was holding a Life Orb, had the ability Sheer Force, and had a Modest Nature. Its moveset was comprised of Thunderbolt, Flamethrower, Earth Power, and Sludge Wave.
Nidoking
"I love Ferris wheels. The circular motion… The mechanics… They're like collections of elegant formulas."
N
If a Pokemon at the front of the party has one of these three abilities, there's a 50% chance the wild Pokemon will be in the upper bound of their encounter level range.
Pressure, Vital Spirit, Hustle
In Generation I, this move divided your crit rate by 4 instead of increasing it like it was intended to. In Gen I and Gen IV, it is affected by Haze.
Focus Energy
In Gen V, this Pokemon was given out to tribute the 2012 VGC World Championship winner, Ray Rizzo
Metagross
In 2014, Verlisify posted a video featuring a set for this Pokemon. The Pokemon was holding an Eviolite, had the ability Infiltrator. Its moves consisted of Toxic, Roost, Defog, and Confuse Ray. In the description, he said he forgot about Super Fang.
Golbat
"Oh, c'est fantastique! This is where you practice dancing, non?"
Fantina
After winning a battle, a Pokemon with this ability will have a chance to pick up a specific item. The chance of picking up this item depends on the user's level, starting at 5% from levels 1-10, increasing in increments of 5, ending at 50% from levels 91-100.
Honey Gather
In Gen IV, using this move and then sending out a Pokemon with King's Rock will activate its effect, causing it to be able to make the target flinch.
U-Turn
This Pokemon learns Draco Meteor from events in both Gen IV and Gen V.
Jirachi
Verlisify posted a video in 2015 where he featured a set for this Pokemon. This Pokemon was holding an Eviolite, had the ability of Friend Guard, and moveset of Follow Me, Helping Hand, Icy Wind, and Protect.
Clefairy
"Did you have a part-time job at the Poké Ball Factory to pay for that ugly suit?"
Calem
In Gen IV, if a Spinda encounter was forced by this ability, it will have one of 50 patterns.
Cute Charm
In the NetBattle days of Gen III, a programming error led to this move blocking Rapid Spin
Substitute
In Gen I, these two Pokemon could learn Pay Day through a Japanese-exclusive Pokemon Stamp campaign.
Fearow & Rapidash
In 2014, Verlisify uploaded a video featuring this Pokemon. This Pokemon ran Leftovers and had the ability Thick Fat. Its moves consisted of Stockpile, Toxic, Protect, and Drill Run. Despite Drill Run being its only attacking move, Verlisify ran it with a Calm Nature.
Dewgong
"I came to see what was taking so long to snatch some parts, and you simps are held up by a mere child?"
Archie
If a Pokémon with this ability is in the first place in the party (even if fainted), the wild Pokémon encounter rate increases by 100%, but it does not effect the Rock Smash encounter rate.
Illuminate
In Gen V, if the player sends out a Pokemon with one of these abilities, the enemy AI will act as though all Pokemon the player sends out after also have the ability unless the on-screen indicator is shown.
Levitate, Water Absorb, Motor Drive, Flash Fire
This Pokemon was able to learn Encore due to the PokePark Egg Event that lasted from March to May 2005.
Cacnea
In 2014, Verlisify uploaded a video featuring this Pokemon. This Pokemon ran a Life Orb and had the ability Technician. Its moves consisted of Taunt, Play Rough, Fake Out, and Return.
Persian
"What I was missing until now... Battling with you made me realize what it is. That's how I feel. You're a mysterious Trainer."
Clair