For synths it's Omnisphere and Synth1. If I can't get it between those two, I'm doing something wrong. I occasionally whip out the orig PPG emulation. I have a real one, sitting in pieces, in a storage facility. The plug in sounds as good, certainly in a live situation. (And MUCH more reliable)
Metaplugin is simply great. It allows hosting of VST3, provides a patch cord modular type GUI and allows me to port setups from my DAW to Cantabile and back again. Until we get rewire, this is my solution. It also solves a lot of connection issues which are not so easy to program in Cantabile, such as wiring one sideo of an amp into speaker sim and the other side somewhere else. You just wire it, done.
The Blue Cat stuff is very useful indeed - especially the volume plugins.
PLZ midi collection. Free and beautiful utilities that just make things happen that would be impossible without.
Of course, that GSI stuff, VB3 and I do like their Rhodes as well. Stick it into the right amp sim and it's alive.
Scuffham S-Gear and Guitar Rig and ReCabinet along with the other freebie amps. You can pretty much dial in any guitar sound these days.
Sample playback from Kontakt and Halion 4.