I always had a fondness for Barkhorn's and Eila's emblems. Barkhorn's most of all, I dont know why, I just seems so awesome to me. But Minna and Mio's are tied for 3rd in my book.
The thing that amazes me is that it's actually a twelve-frame calendar. Unless things have swung back that way or something, all most all the anime/manga calendar I ever see are two-month, six-frame calendars.