My freshman year at Indiana University School of Music, I got thoroughly obsessed with Der Rosenkavalier. The opera theater was doing it (they prepared for it most of the year), and I attended most of the orchestra rehearsals and all of the performances. I was drunk on it, couldn't get enough of it. And I went on about it at most of the meals in the dorm too; my friends deserve a medal for being patient with me and not avoiding me during that period of infatuation.
I've seen regrettably few of the operas onstage (Rosenkavalier, Ariadne auf Naxos, Frau ohne Schatten, plus Capriccio in concert -- from the BBC box at the Albert Hall!), several more on video, still others on recordings. I also love a great deal of the orchestral music (Don Quixote and Till Eulenspiegel at the head of the list), and many of the songs, especially those with orchestra.