Airborne/Spaceborne or Naval craft that are big, heavy and slow.
Do We Have This One? On land, tanks are fairly common. At sea, in the sky or in space? Not so much... at least, not in reality. Sometimes, speed is traded out for size and the ability to take a beating. This trope doesn't specifically refer to capital vessels (e.g: The Battlestar), but most of them do fall under this umbrella.