Oh, I almost forgot:
Rogue Amoeba Soundsource
It's such an integral part of my sound (coraudio) management, and just sits in the menu and quietly does its job.
It gives me back volume and mute control from F10 F11 F12 keys that often is lost with installing an audio interface/driver. And gives me:
Independent routing and volume of in and out and soundeffects.
Independent routing and volume for individual apps.
Ability to insert AU plugins on app-by-app.
Runs with PT flawlessly and manages samplerate differences automatically.
And lots more.
(I actually have most apps set to about 40% volume, and PT set to 100%, which gives me a nice balance and lots of headroom in audio coming from PT.)
Of course, this only works with Coreaudio interface.