Groupon While the website never really appealed to me, Groupon's apps and the Groupon Now service is ridonculous. I could pass by a store or bar or whatever and get notified if there is a sale going on at that particular moment. Pretty sweet.
Amazon Mobile If I could only have one shopping app to choose from, this would be the one.
Watch with eBay This one is pure genius. Sit on the coach, load your cable/satellite information into the app, let it know what channel you are watching, and get presented with related merchandise you can buy with a tap of the finger.
Yowza!! Mobile Coupons A pioneering mobile coupon app that remains relevant nearly four years after it debuted.