I know the Octatrack has been mentioned, but since the question mentions filters specifically, I think it’s worth talking about.
I like the controls we get on the OT filter: base frequency, width, drive, resonance for either (or both) low or high pass, attack/decay envelope. The envelope also has a few modes for controlling when it restarts its cycle.
And most importantly I think it sounds great. It’s very “musical” for lack of a better word.
I like the rest of the effects on the OT, with the exception of the spring reverb – personally I only use the plate and dark reverbs… And I mostly use the plate to abuse its gate.