Liltotto Lamperd (Bleach) eating any matter, as The Glutton.
Like most Boulder-class dragons, Gronckles (How to Train Your Dragon) are able to injest nearly any type of metal and mineral, their furnace-like stomachs able to melt it down into lava.
Like most boulder-class dragons, Hotburples (How to Train Your Dragons) are able to ingest almost any kind of mineral or metal. Hotburples are especially acceptional, as they are the only type of dragon that can eat through the iron-ore of dragon-proof metal.
The Giant (The Iron Giant) consumes metal for sustenance.
The Great Devourer (Lego Ninjago) consumes all it comes across.
B.O.B. (Monsters vs Aliens) is able to digest nearly any form of matter, ranging from organic food to cement and metal.
Thanks to the Baku Baku no Mi Wapol (One Piece) can eat practically anything without harming himself. Such things include knives and cannons.
The Ultra Beast Guzzlord (Pokémon) is able to devour entire oceans and mountains without leaving any waste products behind at all.
Despite his small size, Aron (Pokemon) can eat an entire mountain