1966 because it was really ND proclaiming that "We are back baby" after 5 straight seasons without a winning record from 1959-1963. The 1964 team was robbed of a national championship, but '66 came through!
1973 because I was a junior then, and to live through such a great season, especially since I was working in Ann Arbor at the time, for me was just the greatest.