The Mid-Side Control panel by Tek’It Audio.
Spacial / Mid/Side Effect.
This one gives you the haas effect. Suprise!
The “preFIX is a pre-mixing and audio alignment tool” that allows you to correct some basic issues and covers “frequency correction, phase alignment, spatial stereo field corrections and routing”.
Analog style modelled signal designer.
Blue Cat Audio provides this simple but very useful gain tool for free.
M-ST. A cryptic name for a cryptic plugin. It can convert Mono to Stereo to “wide” and back.