Pressure

In battle
Pressure doubles the foe's PP usage for every successful hit. This ability works even if the Pokémon is immune to the attack's type, for example, using Earthquake against a Flying-type Pokémon.

As of Generation IV, one is alerted to the presence of Pressure by the message " is exerting its Pressure!" Outside of battle

Outside of Battle
If the Pokémon with Pressure is leading the party, then Pressure increases the chance of battling a higher-leveled wild Pokémon by 50%. See also Hustle and Vital Spirit.