The "Ship of the Week" header over at Andrew Duppstadt's blog Civil War Navy is a constant reminder that the Civil War years saw perhaps the weirdest array of naval architecture in the history of warfare, from revolutionary original designs to perhaps less well thought out conversions. My personal favorite is the ironclad U.S.S. Choctaw, reproduced wonderfully by artist Tom Freeman and shown here gracing the cover of the U.S. Naval Institute's Naval History magazine (June 2006 issue). It has my vote for both the strangest and coolest of Civil War warships.
Note the U.S.S. Lafayette (pictured below), similar in design to the Choctaw, but with enlarged casemate. Publications often confuse the two vessels.