in blender 2.53 the knife tool only has a freehand mode for specifying where the exact knife cut takes place. this ehancement would give the ability to move in a straight line basically from point a to point b.
Usage:
press K to enter knife mode pressing left mouse button will set the initial point to start the line from, dragging the mouse would extend the line to where the user desires, left clicking once more will set the end point of the line and will create the cut. enter will apply the cut.
modifiers would be ctrl to enter into either grid, or snapping mode depending on what is currently set.
Contact me for whatever model requests you would require for this.
bonus points for constraining to x y z global axis and maybe stored transform orientations.
