I for one, still find it cool that after 500 years of watches, KV was the first one to come up with the idea of a decimal repeater -- would love to know of an earlier example, but I'm not aware of one.
Then there's Volker and the hard linkage of seconds hand to minute-hand position (if he can get it to production)...
At least one other that I was thinking of when I started typing this, but it's slipped my mind! (advancing age coupled with Christmas dinner wine, I suppose!). Oh yeah -- the JLC use of the "third face" of the Reverso cradle to contain a perpetual calendar display fueled with a single pusher from the main Reverso case. I have a professional interest in these moments of orthodoxy-breaking insight, and would have loved to have been a fly on the wall of the JLC design team when someone came up with that one.
I actually asked Kari how he came up with the decimal repeater idea, and he said that he didn't remember! I'm guessing that modesty was at play, but would welcome any other reports/insights on this one.
I also find the Halter Barnes story interesting and little-explored -- almost as if it didn't really happen, although it clearly did!