My default project template's chain is Pro-Q -> Ozone -> SPAN, but it doesn't always stay that way.
I'll customize my mastering chain depending on the song, so no two projects are alike. Ozone will be in there maybe 60% of the time, although I may substitute Pro-L for limiting and Saturn for its harmonic exciter. I almost never use Ozone's EQ anymore, and the stereo widener only rarely.
Nowadays MSpectralDynamics will almost always be in there somewhere, but not necessarily on the master bus. Taking a look at my current project, I see I have only Pro-L on the master, just to catch stray peaks. All the action is happening on individual busses:
instrument bus: Pro-Q -> Saturn -> MSpectralDynamics -> Ozone
vocal bus: MDynamicEQ -> Pro-C
(why both? Pro-C is just for de-essing)
drum bus: Pro-L -> instruments bus
master: Pro-L, no boost, only sporadic compression on a few loud drum hits
It may seem strange to have two instances of Pro-L in series, but they're doing two different jobs. The one on the master isn't doing much at all, it's just my goalie.
Yesterday's project was quite different:
instrument bus: Pro-Q -> MSpectralDynamics (used for ducking, not EQ)
vocal bus: naked
drum bus: naked
master: MSpectralDynamics -> Ozone
Pulled up one from three days ago, it's different, too:
instruments: Pro-Q -> Pro-C -> Ozone -> MSpectralDynamics -> MDynamicEQ
(Why two equalizers? MDynamicEQ is not used for EQ, but for ducking)
(Why Pro-C and MSD? The first is for M/S widening, MSD is for spectral smoothing)
vocals: Pro-C -> MDynamicEQ
drums: Pro-Q
master: MCompressor -> Pro-L
I sometimes wonder why I can't be more consistent. It would simplify things. But no two songs are alike.