Panzer VIII Maus
Panzerkampfwagen VIII Maus ("Mouse") was a German World War II super-heavy tank completed in late 1944. It is the heaviest fully enclosed armoured fighting vehicle ever built. Five were ordered, but only two hulls and one turret were completed before the testing grounds were captured by advancing Soviet military forces.
Hulk (ship type)
Several of the largest former oil tankers have been converted to floating production storage and offloading (FPSO) units, effectively very large floating oil storage tanks. "Knock Nevis", by some measures the largest ship ever built, served in this capacity from 2004 until 2010. In 2009 and 2010 two of the four TI-class supertankers, then the largest ships afloat, "TI Asia" and "TI Africa", were converted to FPSOs.