A couple things to try below:
Harmadillo: Set everything to 0, Set X over to min or max value, Depth 100, set Shape to one of the pulse options. Once you have a sound you like start adjusting the other parameters to find some cool sounds.
TremoloPan: Depth at max value, Shape set to square, Spread set to 0.
Undulator: Intensity and Depth at max value and Shape set to square.
You may have luck with Aggravate which has a great Pump control but there will always be a bit of distortion added.
