Tell someone you love them with Heart shaped cookies and their initials baked right in.
While this Heart clearly has the initials of someone else, you can use the Google Sketchup file to remove the letters and add your own, resize the model.

The trick to a successful cookie cutter is the outside edge. It has to be strong enough to hold and thin enough to cut. The walls of the heart are 0.8mm (2 extrusions wide on the MakerBot - so if you scale up - look carefully at this).