I can't play by these rules, there's too many good reasons not to.
Dirt, just a bit. Before, to change the sweep of the filter, push it harder or sweeten it up a bit. Having some extra Treble is always good.
Synth OSC before. Subterranea, or any other robot fart sound. You get instant synth like sweeps.
Compressor before to change the sweep action and create a repeatable sound regardless of over excitement.
Yup, another filter, gets vowel like and just so thick.
A swell pedal or tremolo, so the filter become an LFO triggered version of sorts.
After: delay, reverb, swell pedals, dirt and just about anything else.
Actually anything before and or anything after makes for a useable sound inone way or another- especially if you can sweep the filter with your foot - in the case of an auto filter you turnt he sensitivity down, and ride the frequency knob.!