Turns your instrument into a synth. I used this with my electric violin and liked it a lot, to the point that I eventually added an actual synth to my rig and don't have room for it anymore. It's basically a small synth in pedal form.

Multimode filter with cutoff, resonance, and shapeable envelope
Portamento and sustain controls
Modulated delays
Mono, poly, and arpeggiated synth modes with multiple waveforms