If you are looking for tools like EQ, compressors, etc. Waves, Sonnox, McDSP, are amongst some of the most popular and most used in our suites.
As for reverbs, Altiverb, Waves Trueverb/Rverb, Sonnox reverb, are amongst some of the favorites
But I usually have a lot of fun with stuff like OhmForce, and some cheap or even free pluggos! internet is full of those nowadays.
Why? Well, grown used to use waves on a regular basis specially compressors. Don't seem to find much different between most EQs (there are some eq's that are completely out of main stream out there) and I'm usually not to fussed about it unless I specifically want something not usual or if I want a Lin-phase EQ. Compressors on the other hand seem to have such different behaviour between themselves that I tend to not make a decision until I went through a good amount of them. McDSP are good on this too, so are Sonnox.
If you have some money to splurge, the UAD cards offer some pretty sweet stuff. Their reverb is outstanding imo! Had the chance to use a plate rev once but I don't think I would go to the trouble of carrying those tanks when I have the UAD one!
Having said all this, mixed several albuns with the Digirack plugins alone (included in ProTools).