I have fond memories of the Mac Plus disk scan sound and startup beep as a kid. But then one day, the computer delivery guy came by with a Mac Centris 660AV, set it up, and turned it on. The orchestral chime blew my freaking mind. I literally felt hairs standing up on my neck.

edit: The Mac Plus sounded like the "Macintosh SE" file, and the Centris is marked as Quadra AV there, since they renamed the Centris line later.