batsbrew
so, 
when you guys say 'ozone',
isn't that a suite of plugs?
 
i'm looking for a single plug...
such as 'maximizer', or 'dynamic eq', 
that kind of thing.
 
 

Ozone is both.  It can be used Standalone, or as a plugin,
and each of it's modules can be used as individual plugins
in Advanced....

ok, so with ozone,
which is your favorite and most used module?
 

Yes, Ozone Advanced is actually 21 (!) separate plugins.
 
I'll still cite "Ozone" as my one favorite plugin, though. It is just one item on the plugin menu.
 

batsbrew
ok, so with ozone,
which is your favorite and most used module?
 

That would be a tough call...

Might not be the type of plug the OP had in mind but Amplitube 4.

Glyn Barnes
Might not be the type of plug the OP had in mind but Amplitube 4.

Interesting....Glyn, how else do you use A4 (besides as an amp sim)?

Since I chose Izotope, I will state that I have Izotope products for the presets. Get me in the ball park and I can fine tune. Give me a window of knobs to twist without a preset, and I am clueless.

I have to go with Slate Digital Trigger. Waves Linear Multiband is a close second.
 
Rocky

EDIT vote: 
 
Jamstix 3
 
Pretty much any other plug in there is a legitimate alternative.  I'm not aware of anything on the PC side that does what Jamstix can do.

Mesh

Glyn Barnes
Might not be the type of plug the OP had in mind but Amplitube 4.

Interesting....Glyn, how else do you use A4 (besides as an amp sim)?

Nothing too out of the ordinary. I usually have a few amp sims in a project and mostly its Amplitube. as I am using Pro Channel for most of the EQ and dynamics etc. It's my most used non Sonar plugin and the one I would most hate to loose.
 
I use Melda effects plugins a lot but could nopt narrow it down to one.