If we're talking big guns, beat this one! Reputedly the largest muzzle-loading cannon ever made, it weighs 102 tons and has a bore of 17.72 inches. Built by Armstrong, four were installed in the Mediterranean in the 1880s to counter the threat of the Italian battleship Duilio - two at Gib and two at Malta. This one, at Fort Rinella, Malta, luckily survived.
Rick