Unburden
17 Pokémon can have Unburden: 10 as a regular Ability and 7 as a Hidden Ability.
What does Unburden do?
When this Pokémon uses or loses its held item, its Speed is doubled. If it gains another item or leaves battle, this bonus is lost. This includes when the Pokémon drops its item because of Knock Off. This bonus does not count as a stat modifier. There is no notification when this ability takes effect.
Which Pokémon have Unburden? (10)
Which Pokémon have Unburden as a Hidden Ability? (7)
How Abilities work · Hidden Abilities explained · Every Ability