At first I was going to suggest that the waveform could be selectable in the tremolo effect, but had a better idea, so here it goes: the chopper effect would produce a harder effect than the tremolo because instead of a sinus or triangle waveform it would abruptly cut the sound (depending on the depth parameter setting) using a square waveform. It would have the usual pulse width parameter which determines the percentage of the waveform on the positive half of it, but why stop there? I thought it would be interesting to spice things up a bit by adding 4 "switches" that would allow for producing some very interesting rhythmic patterns (think Fruity Loops).
So the parameters would be:
Time/speed: in seconds or hertz, and would be syncable with tap tempo/MIDI clock
Multiplier: 1/2x, 1x, 1.5x or 2x (relates to the above and would be really only useful when using tap tempo/MIDI clock)
Depth: depth of the effect, how much it "cuts" the sound
Pulse width: the percentage of the square waveform it stays open or closed (sound is heard/not heard)
Switch1, Switch2, Switch3, Switch4: each one of these, when ON will cause the effect to be applied on that slot, when OFF there will be no effect in that slot.
Note that a traditional, simple chopper effect would be achieved by using pulse width 100%, switches 1 and 2 ON and switches 3 and 4 OFF.