I've never used a rotary cutter so can't comment on that. For rectilinear shapes, I use a paper cutter to avoid drawing guide marks on the paper. (I just go by the ruler on the paper cutter.) For common rounded shapes, like circles, ovals, hearts, etc., I use craft paper punches as noted above. It's hard to get as perfect shapes by hand-cutting - plus, punching is MUCH faster if you're doing a lot. For all other shapes, I score/trace the shape (using a turkey lacer) with the paper on top of the cookie to match the cookie icing as best as possible.