One of three reasonable choices for the top spot in the composer category, but this happens to be the choice I myself would go with. Usual mentions Fur Elise and Moonlight Sonata, but probably it's the Fifth Symphony, as overplayed as it is, which is his single greatest contribution, and the most well known piece of music ever composed.
I have to leave for quite some time, will update when I return.
I actually like the 9th Symphony with Ode to Joy in it better.
Freude, schöner Götterfunken,Tochter aus Elysium,
Wir betreten feuertrunken,
Himmlische, dein Heiligtum.
Deine Zauber binden wieder,
Was die Mode streng geteilt;
Alle Menschen werden Brüder,
Wo dein sanfter Flügel weilt.
Deine Zauber binden wieder,
Was die Mode streng geteilt;
Alle Menschen werden Brüder,
Wo dein sanfter Flügel weilt.