bitflipper
Most useful effect plugin ever bundled with SONAR: Channel Tools. 
Most-used feature: CTL-Z.

Dave,
I am with you on your list, but those two are definitely top for me.  What feature I really like is clip effects.  I wanted that for a long time (like the Channel Tools) before it was implemented.
 
Also, I use the Matrix View quite a bit, albeit it can use an update with more features.  I was a P5 user along side SONAR, so I am glad they integrated a loop/pattern trigger/player like the GrooveMatrix in SONAR.  I use it to playback a music bed while I record and improvise without having to set and loop in the time line.
 
Kind regards,
 
Living Room Rocker

dubdisciple
The ability to bounce arpreggiator to midi notes that can be edited. Arpreggiators are great but can be stiff and monotonous. Being able to instantly render out all that is heard from pressing one note or chord opens a lot of flexible ways to edit and add variety.

Mind.....blown. How?

BCnSTL

dubdisciple
The ability to bounce arpreggiator to midi notes that can be edited. Arpreggiators are great but can be stiff and monotonous. Being able to instantly render out all that is heard from pressing one note or chord opens a lot of flexible ways to edit and add variety.

Mind.....blown. How?

Best part is it is simple. Just right click on the midi clip on a track that has the applicator active and choose bounce to clips and a new midi clip will appear that has all the notes.

I'm a groove clip looper lover.. And a bounce clipper
I love the media browser , grab a loop a sample drag it into the time line , right click on the sample or cntrl L it . Drag it out for sequencing , or Bounce it to clips, cut it up with another sample then bounce that to clips than groove clip it again , drag it out 8 bars then bounce that to a clip ..
For me Bounce to clip and groove clipping goes hand in hand for me.. This is a feature I use relentlessly.

Great thread..

arachnaut
I like to undock the browser, go to the VST plugin and open up the controller assignment to add automation knobs for the synth.

This is pretty cool. I've never done it before. The first thing I tried to do was get it to work with touch, but it was pretty awful. I do like to use touch with rapture and dim pro. It really works well directly in those synths.
 
If touch was better implemented in the controller assignment I'd probably make use of this in part because it is space efficient.

If you use Melodyne to fix pitch and timing, while you are there, use the amplitude tool to fix notes that are too loud or quiet so you don't have to over-compress. You can highlight and change groups of notes, too.

The F key shortcut to view all tracks. Autozoom highlighted track. PC flyout EQ, PC breverb. The cool synths are Zeta +2 (upgraded), Dim Pro, Rapture , AD, strum and EP lounge lizard(upgraded). I don't see why I need to look elsewhere (Abelton, FL or Reasons) for my MIDI needs.

Anderton
My favorite underrated plug-in is the Sonitus Multiband compressor. Not only does it have the limit feature so you can do "maximization"-type compressing (as long as you don't take it too far), but if you don't use it as a compressor by setting the ratio at 1:1, it's a great multiband crossover - insert it in the effects bin and solo a band to process only that range of frequencies.

There are other great uses for the Sonitus Multiband as well.
 * De Esser - Just tune the high frequency band to where the problem is and compress
 * De Plossive - Just tune the low frequency band to where the problem is and compress
 
The great thing about using a multiband comp for plosives, is that you can leave the low frequency untouched until a plosive comes along, and kill it with compression rather than need to change the EQ of the rest of the material.  Also works great for wind noise suppression.

I'm gonna go with the percussion algorithm in Melodyne (so I can see the blobs linearly) in conjunction with the volume tool. I use this all the time now for leveling vocal tracks - way more transparent than compression alone. I used to do this by splitting vocal tracks up into a bunch of clips and changing the gain of the individual clips. Now I can just adjust the volume of the blobs in Melodyne and, what's even cooler, they are resized to represent their new level, whereas the waveforms of clips stay the same size unless/until you bounce them.

+1 for PerfectSpace