I've had silkies, BO, RIR, SLW, BCM, and RSL. Of these the silkies have gone broody an awful lot, but of my birds the buff orpingtons are hands downs the broodiest birds I have. I refer to one as "stupid broody" because she goes broody at least three times over the summer and sometimes in the winter.
I do however, have a small flock, and limited experience. Because of the neighborhood, I can't afford anymore roosters, so the broodies don't get eggs to hatch. Stupid Broody managed to kill two of the three chicks she successfully hatched out....stupid broody!