The plugins I've been using lately have changed dramatically from when I started mixing. Sometimes I'm guilty of buying into hype, but I've started to discover what I like. And I'm always waiting for it to go on special...
So what makes a good plugin? For me, it's less is more: less options, less possibilities to twiddle, and less graphical EQ curves. Sight is a strong sense, and it can fool even an experienced ear.
PSP Audioware McQ - This 4-band plus high/low filters isn't a true analog modeler, it's a hybrid. But it sounds great, is easy to use, and doesn't hit your processor hard. So really, it's safe to put on just about everything. Its bands are hard to read (Why is it ".10kHz" instead of "100Hz"?), but they're highly controllable. So you can do both broad strokes and somewhat detailed surgery.
Waves API 560 - Under ideal cirumstances I'd have the whole Waves API 500 series bundle, but this one went on sale. It's fun to have a graphic EQ sometimes, especially one with only a few bands. It sounds great on a wide variety of sources too.
Waves Scheps 76 - Another modeler, this one after a console. The gimmick is the integrated preamp. The bands aren't fixed on this EQ but the knobs have huge steps so you can only dial in a few possible frequencies each. The Qs are not variable. It sounds great on drums, especially kicks. Given those few bands, it's easy to crank the 60Hz and then throw one on the bass and drop the 60Hz there so they don't fight. The preamp section can add smooth overdrive to the bass as well.
Maag EQ4 - An incredible EQ. It's got four fixed bands, a fixed Q, and some frankly weird frequency choices. But those bands were supposedly picked to cause the least amount of phase effects. It sounds absolutely magical. It's possible I bought into the hype with this one, but I got a deal and I can't say I feel any regret. I do feel almost guilty using it though; it requires barely any thought to make vocals, acoustic guitars, and even some drums sound amazing.
Nomad Factory PulseTec - Nomad Factory is the Rodney Dangerfield of plugin companies. I'm not sure if this thing sounds remotely like a real Pultec but it goes on all my master busses. It was completely bonkers to me at first to be able to simultaneously boost and cut the same frequencies, but man it does the trick. Not great on the top end (the Maag can handle that), but it thickens and tightens mids and low-mids.
Tokyo Dawn Labs SlickEQ - Another super transparent phase-free EQ, but this one is geared toward the master buss and costs nothing.
Waves CLA-76 - I waited a great long while for this to go on sale. I've always wanted an 1176 that wasn't the Bomb Factory BF76 that comes with Pro Tools. It's everything I wanted it to be and I use it everywhere — primarily drums but it'll tame a problematic source quickly and with character. At its full price, it probably still wouldn't be bad.
Waves Renaissance Axx - I wonder how many people use this thing. I mean, everyone's got the Native Power Pack, right? But Renaissance Axx is one of those tools that feels like cheating. Just slide the threshold down and watch it magically even out guitars and basses. It uses so little processor I get pretty generous slapping it on guitar tracks. I've heard a few pros cop to using this thing and why the hell not?
T-Racks Opto Compressor - IK Multimedia is another company that gets a lot of poop from people. But I've had their opto compressor for a long time and it's one of my favorite tools for vocals. It can open up a weak track by an inexperienced vocalist who's all over the place or who didn't project. You can get miles of compression out of the thing with much more transparency than an 1176. Sometimes I'll double a difficult vocalist's track, overdrive it, crank the mids and highs with a smooth EQ like the Maag, and then flatten it out with this compressor. Mixing in a little bit of that adds presence and is probably a super old trick not worth mentioning. But this is a good comp to do it with.
Tokyo Dawn Labs Kotelnikov - I'm still learning this feedback compressor, but it's smooth and transparent. You almost have to watch the meters to see that it's compressing, but it can make the master buss sound great. And though you can spring for the "Gentlemen's Edition" (?), the basic version is super great and costs zero dollars.
DDMF The Strip - This is actually a full channel strip so it's both and EQ and compressor, in switchable order. It has a Neve look and that's the starting point for the modeling. But this amazing plug goes a little farther into original territory than most models. DDMF is one of the few developers who can get away with charging next to nothing for plugins yet still get respect from GearSlutz. I got it for $30 as a launch special and I'm crazy impressed. Even the knob motion reveals just how much thought went into this. The developer is also a mixer, and it shows.
Flux Bittersweet - Sometimes you need simple transient shaping that'll get the job done without interfering with other dynamics processing. How's one knob? How's free? It sounds nice too.
Blue Cat Patchwork - The Blue Cat folks make some great stuff. This is a simple but flexible plugin chainer that gives me solid performance loading VSTs or AU plugins into Pro Tools. DDMF's Metaplugin would also do the trick, probably very nicely as well.
Blue Cat FreqAnalyst and IK T-Racks Meters - With these two free metering tools, I can monitor what my sound "looks like" for the low cost of free.