I'm a big fan of silhouettes, so I'm loving these shadow puppet chocolates from Food Flower Style. Yes, those are actually shadow puppet designs traced and cut out of parchment paper, and then used as chocolate molds. You can use the same concept for any sort of design, although the shadow puppet idea is really cute. (Unfortunately, this post is no longer on the Food Flower Style site, but I found a copy right here.)
If you're interested in making silhouette cookies, like the ones below that appeared in Martha Stewart Weddings, The Victor Trading Company will create a personalized silhouette cookie cutter for you (see below). Just send them a photo and you'll get a customized cutter ($30) in return. Click here for more details.
For another type of silhouette cookie, check out the these slightly more traditional cookies courtesy of The Good Apple and then click here for tips on making them.