Couponia is the best solution for selling coupons or any kind of goods. It can be used as coupon website (such as groupon.com) and also as online store. Modern, simple and unique design. It will amaze your clients and users. Huge amount of demo homepages (7 for coupons and 6 for shop), and lost of features will help you to make your website really unique.
Demo: http://themeforest.net/item/couponia-coupons-online-shop-template/8233607