Love the Three Sisters filter - very versatile. Sometimes it’s hard to decide if I want to use it as a filter or sound source. Self patching can get crazy too, as with most Mannequins stuff.
The Pittsburgh Modular filter (v2) is my other filter. There’s some quirky things it can do with the oscillator mode, depending on what you put into it and how high the resonance is. It also has an odd vca-like feature that I’m still trying to figure out how to use. Talked to Richard from Pgh Modular and he said that Lifeforms Binary is similar, but lacks that gain of 1(vca-ish) mode and doesn’t scream quite as much in the Oscillator mode (unstable).
I’ve also had a Pittsburgh LPG/filter which was nice, but wasn’t indispensable in my rig. I kind of miss that one though.
Filters that I’ve considered trying in the future: Xaoc Belgrad (lotta hp though), Grendel Formant filter, MI Ripples.