Emerald has added yet another bit of interesting additions...this time to the Abilities. Several Abilities have a few added extras. Below is a list and click each Pokémon for their Dex entry.

Intimidate & Keen Eye

The Ability Intimidate lowers Attack and Keen Eye prevents the lowering of accuracy. Well in Emerald, they both also, if you have them in your team, make Low Level Wild Pokémon less common

Intimidate
Keen Eye

Hustle & Vital Spirit

The Ability Hustle raises Attack but lowers Accuracy and Vital Spirit prevents the user from falling Asleep. Well in Emerald, they both also, if you have them in your team, make High Level Wild Pokémon more common

Hustle
Vital Spirit

Pressure & Arena Trap

The Ability Pressure doubles the usage of PP by Opponent and Arena Trap prevents opponent from running. Well in Emerald, they both also, if you have them in your team, make Wild Pokémon more common

Pressure
 
Arena Trap

Suction Cups & Sticky Hold

The Ability Suction Cups prevents you from being forced from battle and Sticky Hold prevents your hold item to be knocked off. Well in Emerald, they both also, if you have them in your team, make Pokémon easier to catch when fishing

Suction Cups
Sticky Hold

White Smoke

The Ability White Smoke prevents stats being lowered. Well in Emerald it also, if you have them in your team, make Wild Pokémon Less Common

Sand Veil

The Ability Sand Veil raises Evasiveness in Sandstorms. Well in Emerald it also, if you have them in your team, makes Wild Pokémon less common while in a Sandstorm

Static

The Ability Static can cause Paralysis on opponent if stuck with a Physical Attack. Well in Emerald it also, if you have them in your team, makes Electric type Wild Pokémon more common

Magnet-Pull

The Ability Magnet Pull prevents Steel Type Pokémon from leaving Battle. Well in Emerald it also, if you have them in your team, makes Steel type Wild Pokémon more common

Synchronize

The Ability Synchronize copies any Status Inflictions to the opponent. Well in Emerald it also, if you have them in your team, makes Wild Pokémon with the same nature as this Pokémon more common

CompoundEyes

The Ability CompoundEyes raises user's Accuracy. Well in Emerald it also, if you have them in your team, makes Wild Pokémon holding hold items more common

Cute Charm

The Ability Cute Charm causes opponent to be Infatuated after contact if it is of an Opposite Gender. Well in Emerald it also, if you have them in your team, makes Wild Pokémon of the opposite Gender more common

Hypercutter

The Ability Hyper Cutter prevents User's Attack from being lowered. Well in Emerald it also, if you have them in your team, makes Cut's Cut Radius larger

LightningRod

The Ability LightningRod causes Electric Type attacks to hit the Pokémon. Well in Emerald it also, if you have them in your team, the amount of calls Recieved on the Entry Call is increased

Swarm

The Ability Swarm increases Bug type attacks by 50% when HP is low. Well in Emerald it also, if you have them in your team, the roar of Wild Pokémon is more commonly heard