Vital Spirit is an ability introduced in Generation IV. So far, 4 Pokémon have this ability.
Vital Spirit prevents the Pokémon from being afflicted by sleep. Rest will fail when used by the Pokémon.
A Pokémon with this Ability will wake up if it is asleep in battle (such as if it gains the Ability outside of battle or by an effect like Skill Swap, or is put to sleep by a Pokémon with an Ability like Mold Breaker). If the Pokémon is holding a Chesto Berry or a Lum Berry, it will be eaten before Vital Spirit wakes up the Pokémon.
If a Pokémon with this Ability is drowsy due to Yawn, the Ability activates when it would fall asleep and keeps it awake.
Outside of battle
Pokémon with Vital Spirit