Are those the rare items obtained from the Eco-Uwasatchi triplets at the park on the first of the month?
The eco chopsticks, eco fork, and eco bag will give you discounts on items from the restaurant, cafe, and TamaDepa (or is is TamaMori?), respectively, I do believe (though I may be wrong on which one gives you what discount).
When you select the items from the "rare" list, and your Tamagotchi stands there admiring it, the Tamagotchi character will actually receive a boost in happiness. Its happy bar will increase a little without using snacks or games. That's a trick I use when my Tamagotchi is little: If it beeps due to unhappiness, I just select one of my rare items and its happy bar will fill enough to turn off the attention icon.
