it’s definitely become Marbles for me too (see remarks I’ve made on this module uh everywhere else), as Marbles takes the place of a lot of ideas I had in Reaktor and Max/MSP, and generally does in better.
I think Shades definitely deserves mention here (as it already has been), probably never leaving my rack.
a year ago I might have said Telephone Game, which I’m still trying to get back in my rack.