(Whole JPEG is available here)Mentos has recently come out with a mobile promo entitled "power to chews" (from power to choose). It is unique in the sense that the prize you will win actually depends on the day you send your entry.
Also, note how the promo collects the consumers' information, and also sales information. They can be communicated to at a later date, and can be used for analysis.
Mentos also has a pretty cool site, here.
