I've mentioned before how I'm fascinated by my Seiko Coltura Perpetual Calender - and it still hasn't worn off.
When the watch wakes after weeks of sleep, I never ceased to be amazed at the whirling dials and the return to the exact time, day, date etc. And I love that this is kinetic - driven by wrist power like a mechanical automatic - instead of just a battery.
I find myself drawn to it repeatedly since setting the time on my mechanical watches frequently becomes a pain in the butt. Especially if I'm in a hurry.
I love the kinetic and perpetual calendar features (other brands make them I think) and urge all watch geeks to check 'em out. Truly a marvel of engineering - for the lazy, like me.