1. A pop-up notifying the visitor on the website's cookie policy (required by EU law).
2. A pop-up asking the visitor to consent to its privacy policy (required by EU law).
3. A pop-up asking the visitor if they'd like to subscribe to its newsletter.
4. A pop-up telling the visitor that it's run out of "free articles", but that you can sign up at a premium.
5. A pop-up asking the visitor to turn off the adblocker because the site's revenue depends on the ads.
6. A pop-up asking the visitor to participate in an online survey.
7. A pop-up telling the visitor about a unique way to earn money in your underwear.
None of the pop-ups will share UI for closing them, and some of the close buttons will be so hard to press that you accidentally change site instead.
(Clarification: It doesn't have to be a pop-up, but it does have to be annoying.)