Dietrich Fischer-Dieskau
Fischer-Dieskau had a lyrical baritone voice, not a powerful, heroic voice like a Heldentenor.  In spite of that he recorded many operatic roles which are traditionally thought of as being for Heldentenor: Wotan in Richard Wagner's Ring Cycle, Hans Sachs in Die Meistersinger von Nürnberg, Amfortas in Parsifal, Macbeth in Verdi's opera etc.