Blencowe Hall, located in Cumbria, England. A 14th century manor whose towers were left to decay for over 300 years. The large gash in the masonry wall of the south tower is believed to be the result of an attack during the English Civil War.
Monadnock Building (1891) One of the first buildings I think of when dealing with walls, the Monadnock Building. It was, and I believe still is, the tallest building with load-bearing masonry walls. To accomplish this the walls are 6 feet thick at the base and taper to a foot and a half.