Note: this post is from 2008, outbound links may be broken.
Atom Splitter Audio releases Clip-R
Clip-R is a stereo effect which allows you to trim/clip the ceiling (top) and floor (bottom) of any audio you put through it, it also features a boost control which happens before the clipping and can be used to distort the signal in combination with clipping.
The left channel is shown in green and the right in red, the clipping level is show in black and this lets you see exactly what is happening to the signal. The effect works well on basses and basic waveforms like a saw etc and can change the shape.