I forgot one...and it's definitely a "holy grail" filter: the Rohde & Schwarz UBM. However, this ancient tube-driven bit of WDR Cologne's electronic music history (especially in Stockhausen's hands) is VERY screwy. Tubes, of course, are AUTOMATICALLY screwy, but whatever's going on inside these huge gray boxes (I have two) is NOT simple filtering. Push the input, and you get warm, wooly fuzziness. Run up the regeneration control, and the filter first acts LPF-ish, but then gets into a NASTY, ringy passband configuration with that Q rising as the control is raised.
What does it sound like? OK, it's all over this: along with a few other filters, but the UBM handles the bulk of the load on this work. Frankly, I'd love to see one of the tube-oriented Eurorack companies take on a challenge like this...and it could be lucrative, too, given that there's only a finite number of these still in operation and when one pops up, the feeding frenzy gets INTENSE.