A website that lets you create official-looking GitHub links that rickroll the visitor.
Simply replace github.com with microsoftgithub.com. The resulting URL will redirect to the rickroll video, and its social media preview will look identical to the official one.
For example, https://github.com/github/dmca becomes https://microsoftgithub.com/github/dmca.
When I realized this domain hadn't been bought by Microsoft, I decided to purchase it. It was dirt cheap, and I didn't want it to fall into the hands of scammers who might use it for phishing. With the domain in my hands, it would have been a waste not to use it to rickroll unsuspecting people.
To date, 235.3k visitors (excluding bots and crawlers) have been rickrolled, and the number keeps growing!