The late Seigo Yamaguchi and some of his students like Sekiya, Tissier, Inaba, Gleason, etc, have a background in Kashima Shin Ryu kenjutsu rather than the more common Iwama style sword. It helps give their aikido a very different flavor.
Interesting... however, in an interview with Yamaguchi Sensei's famous student, i.e. Endo Sensei, I did recall a strong preference for empty-handed techniques... I remember the interviewer asking him about weapons training, and Endo Sensei replied there was still so much to be done with taijutsu... maybe he wasn't part of the group that took to weapons in a big way?