ironically i did this once for real, bought a 12 pack of shiner bock and a pregnancy test, found the oldest cashier i could find....hilarity ensues....another good two items would be the obvious i'm surprised no one threw out there yet: lotion and tissues
another fun game is to call up walmart, or show up with items that are "slightly used" and try to get them to refund you...underwear, pregnancy tests, a half eaten birthday cake, a used tire, and my personal favorite: go to the store with a can of chocolate frosting and a bottle of liquid ...,
buy a plunger, go back to your vehicle, dress up the plunger with some frosting and spray it down good with the liquid ..., and go back in to attempt a return, stating: it doesn't work.