Free:
Pretty much anything by Bootsy for mixing tools.
Onqel's stuff for pedal emulations. I use his tubescreamer, bass driver and rat clones often, and they never disappoint. Tubescreamer sounds pretty cool on gritty vocal automations, and the rat clone is now my favourite bass distortion (together with a cab impulse).
TLS limiter. I like this one better than some paid limiters. Very transparent.
ReaEQ for surgical cuts.
Cheap:
VibeEQ for colourful boosts; especially the shelves. I only wish it had more frequencies to pick from.
Rocket compressor: fast and gritty if you want it to be. I like how it has the positive traits of an 1176, but also a definite character of its own.
ToneBoosters Reelbus for tape stuff. I own Slate's tape plugin, but still use it here and there.
Klanghelm DC8C compressor. Has an easy-mode and I-love-buttons-mode. Does quite a few different characters very well. Hard to describe the character of this one, but "smooth" comes to mind. In the expert-mode it's extremely versatile, but also a bit daunting to get your head around at first. I strongly recommend to read about how different compressor-designs work to get the most out of it.
The M30 reverb is not bad by the way. I got it for free a while ago on some special they were having. It's only the Hall part of the algorithm, but I use it regularly. My only gripe with it is that it isn't very tweakable. The plus side of that is that it's easy to set and forget. I use it as a tracking verb for vocalists. It's light on CPU and they are more inspired by it, so I'm happy.