Cakewalk's Sonitus fx:Reverb. I don't use it on finished tracks (right now I tend to use NI's RC48, Waves IR-1 or, IKMultimedia's Hall reverb for final mixes), but when I create sketches and test compositions, I use Sonitus as a quick and easy-to-run reverb. So, while it's not a finishing tool, its involved at some point in pretty much everything I do. And for an older plug, it still sounds perfectly decent.

Fleer
No love for Arousor?

 
I demoed it and loved it, but not $300 - $350 loved it.
 
Equick possibly my most used. Shout outs to MJUC and Slate VMR though.
 
 
 

arachnaut
I think I use Reaktor every day.
 

I'll second NI Reaktor.  I've got like 10 instances of Reaktor in my favorite template.  Compression, effects, drum machine, synth.  

Fleer
Rain, where do you keep finding these beauties. I'm thinking you read the manuals.

When I switched platforms in 2010, I decided to do everything I could to ease the transition to my new DAW. These helped speed up my workflow quite a bit. ;)
 

Rain
Besides EQ and compression, I think that the plug-in I use the most is called "Direction Mixer". It's especially useful with virtual instruments and drum libraries which tend to be all over the stereo field - such a plug-in allows one to manage that. I also use it on busses with reverb.
 

 
I'm guessing that Sonar has something similar (which I am anxious to find out for myself the minute the OSX version is released!)

I would like to know an alternative to this. Sonar or 3rd party. Any one?

patm300e
+1 for Sonarworks headphone calibration software.  I have Ozone 4, maybe I should think about upgrading.  There are a lot of happy 7 users.  Now where to come up with $299...

THAT is always the question...

I second much of the above, Toontrack, Celemony, Izotope and more...
 
But what has really been good for me in the past year was IK Multimedia's T-RackS Vintage Compressors Bundle. I am having a wonderful and prolific time writing music these days (style like Loggins and Messina, Livingston Taylor, Jackson Browne, Johnny Cash), based around acoustic guitar and vocals. These plugins really helped me get the sound I have been looking for in a way that I really enjoy. In other words, with some other great software, I feel I need a PhD in Celemoniac or Izotopian physics to "get "er done" and so I enter my mixing sessions with trepidation.
 
Back in the eighties when I first began recording in the analog studios, it was so much fun and opened a whole new realm to songwriting. The rack modules and mixing board made sense to me and it was a sound we were after. I now feel that way again and am looking forward to T-RackS British Studio Series to complement the compressors, and more.
 
So I thought I'd add that to the mix.
 
Of course, none of this would be possible without Cakewalk Sonar and so a shout out to Nick at Sweetwater who recommended this to me long ago is in order. It took a lot of doing to convert this tube head from analog to digital, but my metamorphosis is now complete :)

MStereoSpread looks really cool.

Channel tools - Efficient.

xiwix

arachnaut
I think I use Reaktor every day.
 

I'll second NI Reaktor.  I've got like 10 instances of Reaktor in my favorite template.  Compression, effects, drum machine, synth.  

I would think if you could reach a high level of knowledge of Reaktor you would buy less synths.

Slate's VMR, for sure. I haven't mixed a track without since I got it. I don't use every single module in it, but most of them are indispensable for me now. I subscribe to the Everything Bundle, so I use a ton of Slate stuff all over my mixes, but if I had to choose, VMR would be my desert island plugin. 

Robbyk
 
100% agree! I completely forgot my TrackS plugs! I master all my projects with them and I use them on many channels especially vocals!
 
I can't believe I forgot to mention them! Doh!

Kontakt.