VCAs...well, if you want versatile, Veils has that. The ability to sweep between linear and logarithmic responses is a huge plus, and the design itself is so good that...well, lookit all the clones! But at 10 hp for a quad VCA mixer, how can you go wrong? But if we're talking about only linear VCAs, a big fave is Happy Nerding's 3XVCA. Unfortunately, some butthurt jackass decided it would be a good idea to start a war with Ukraine, so if/when we get more of HN's stuff is very up in the air.
If you have a cab or power supply that has no indicators for the DC rails, I STRONGLY recommend keeping 1 hp open for a KonstantLabs PWRchekr. It's small, it's cheap, and it lets you know if you're having DC rail issues.
Mixing utilities: there's two mixers that I like for altering/mangling modulation signals, depending on how much space I'm dealing with. And those are the Tiptop MISO and Frap's 321. These give the best ratio of usefulness to cost on something that many users unfortunately ignore, that being a way to get a lot more mod signals out of just a couple of modulation modules. Paired with a couple of linear VCAs, this is the quick and simple (and if you use a dual Veils clone VCA to pair with the 321, also very SMALL) way to get at that.
And of course, one of the best purveyors of useful utes has got to be Ladik. 4 (or multiples thereof) hp form factors, cheap prices...that's a win. Especially their voltage "reading" modules, which output a gate depending on the input and module behavior. If you're doing heavy sequencing, or especially generative, their stuff has plenty of the "tricks" needed.