I have a soft spot for the Italian Line's Andrea Doria - the collision with the Stockholm and subsequent sinking in July 1956 is the first major news event that I remember... that's stuck with me all these years. Because of it I became interested in shipwrecks and 20th century ocean liners after reading about it and seeing references to other ships.
Other favorites - Arandora Star, Caronia, Ile de France.
Morro Castle - not necessarily a favorite ship, but her story is spellbinding -
As is the story of the freighter Flying Enterprise - read _Simple Courage_ by Frank Delaney... wow.
Gaithersburg MD USA