Free VST Plugins (Windows only).
Squarer

Squares the signal or multiplies the channels.
Download Squarer
zero-x-ing

Creates a single impulse (Dirac delta function) on every zero crossing in the signal.
Download zero-x-ing
Stereo Noiser

Puts positive and negative values of the waveform on different channels. This causes a widening of the stereo panorama as well as additional noise due to the deformation of the signal.
Download Stereo Noiser