Grond (battering ram)
"Great engines crawled across the field; and in the midst was a huge ram, great as a forest-tree a hundred feet in length, swinging on mighty chains. Long had it been forging in the dark smithies of Mordor, and it's hideous head, founded of black steel, was shaped in the likeness of a ravening wolf; on it spells of ruin were laid. Grond they named it, in the memory of the Hammer of the Underworld of old. Great beasts drew it, orcs surrounded it, and behind it walked mountain-trolls to wield it."
Grond was a battering ram, used to destroy the Great Gate of Minas Tirith during the Battle of the Pelennor Fields. It was named intentionally to evoke the memory of the ancient weapon of Morgoth, the "Hammer of the Underworld".
Peter Jackson's Return of the King: In this film, ram took the shape of the whole wolf's body, instead of just it's head. There are inscriptions on it. Grond appears earlier in the battle than in the book.