Gluttony is an ability introduced in generation 4.
27 Pokémon can have this ability, such as Shuckle, Zigzagoon, Linoone, Pansage and Simisage. For 11 of them it is the hidden ability, usually obtained from events, raids or breeding.
Official effect
Makes the Pokémon eat any held Berry triggered by low HP below 1/2 its max HP.