Being asked a bunch of bullshit up-sell questions at the checkout. The rule should be that you get one question. If the answer is "no," then STFU and don't ask any more questions.
For example, if I don't have a frequent buyer card, it's safe to assume that I don't want to sign up for one. Nor do I want a store credit card, the purchase protection plan, a barrage of emails, to donate to your store's charity, or to give you my mailing address.
I want to exchange currency for goods and services. And I wish to do so with an minimum of bullshittery. End of conversation.