Steadfast

 is a Pokémon ability introduced in the fourth generation. It raises speed when flinching.

Description
Pokémon with this ability raise their Speed stat by one stage when flinched

Pokémon Mystery Dungeon
When a Pokémon with Steadfast has the cross-eyed or cringing status, their movement speed is up

Pokémon with Ability

 * Mega Mewtwo X
 * Tyrogue
 * Riolu
 * Lucario
 * Gallade

As a Hidden Ability

 * Machop
 * Machoke
 * Machamp
 * Scyther
 * Hitmontop
 * Rockruff
 * Lycanroc (Midday form)