
miauu’s Scalpel allows you to interactively subdivide (cut up) geometry by drawing lines.
When you make a cut, it has to originate from a vertex or an edge. You can't create vertices inside faces.
With miauu’s Scalpel you can:
•Snap the cut point to the nearest(to the mouse cursor) vertex (Auto and Manual mode provided).
•Snap the cut point to the center(midpoint) of the nearest edge(Auto and Manual mode provided).
•Snap the cut point along edge’s length to set a precise cut location(in percentages of edge’s length). The smallest percentage that can be set is 0.5%.
•Snap the cut point along edge’s length to set a precise cut location(using the system units). The smallest value that can be set is 0.01 units.
•Make perpendicular cut from vertex to edge or from one edge to another using two different options:
the cut line is perpendicular to the snapped edge
the cut line is perpendicular to the edges from which the cut starts
•Use the default QuickSlice with snapping to predefined angles.
•Use a small heads up display of data related to the current cut point as a position along the edge as a percentage, the two distance values indicating the distance to either point in the cut edge, and the total length of the edge.
•See the options for the tool in the Prompt line.
•Change the values of the Snap Step and the Snap Angle while you cut.
Known Issues:
•The mouse cursor must be over the object you cut when you click with the mouse buttons. Otherwise the clicks will not be detected.
•While you are performing a cut the Snap Step can be changed only using the spinner’s arrows.
Works with Editable Poly objects and Edit Poly modifier.

This is a commersial script. You can find more information here.