Like everyone else said, you're better off really focusing on healthy, maintainable weight loss. Do plenty of strength training, too -- muscle tone will help you look fit and strong, which is always fashionable (unless you're a fashion model, ironically).
Then, you can look a few pounds thinner with the right clothing and undergarments. There are a lot of things that will suck you in, smooth you out, etc so that you look a little lighter. Sometimes a tan helps -- start trying fake tanners early if necessary to find one that works. Some hair styles will make your face look thinner. Also, make sure your clothes for the event fit well (alterations are worth the $) and flatter your body shape.
If you want to lose another few pounds right before the event, you could go low-carb and low-sodium and drink a ton of water for a few days. Maybe even look at one of those short term "cleansing" programs (that will help you lose a few pounds of water and, umm, *waste*). I've never thought it was worthwhile to spend all my time in the bathroom just to lose 5 pounds, but some people do it!