While I grew up a Yankees fan (older brothers, who rooted for the Yanks before there was MLB in LA) and then the Angels ('born' in the same year I was), I have to go with a different team. My oldest brother, whom I idolized, graduated High School in 1972; he and a friend took a road trip; when they came back, my brother gave me an Oakland A's souvenir batting helmet, and I became an A's fan overnight. So: the 1972 Oakland A's.