Robert Preston:
Harold Hill, first and foremost, always and forever. But so much else, too. For me, he's one of those who personifies the best in musical theater.
Never got to see him in person. First sight of him was in the film version of The Music Man. We were at the lovely Florida Theater in downtown Fort Lauderdale on its opening night there, and that's one of a handful of glorious early-1960s movies for which I will never forget the theater and the packed audience and the "occasion" of it all. Everything about the movie and the material blew me away, and I lived and breathed little else (until West Side Story just months later).
I love it all, but special recognition goes to I Do! I Do!. (Nice reminiscence there, DR Druxy.) And thanks to a certain Indiegogo, I now possess a treasured RP inscription on the souvenir program (along with that of a certain co-star, making it doubly wonderful).