The folks over at WPBeginner.com have put together a comprehensive list of the best 404 page designs they have come across from sites using WordPress. This showcase is good for inspiration for your own 404 page, a page which I usually neglect when it comes to WordPress themes. As long as the error shows up, I don’t go much beyond that point. Funny as it sounds, I tend to favor humorous 404 page designs instead of helpful ones. One other good bit of information is the list of tips that WPBeginner provides in order to add helpful information to the 404 page template within your WordPress theme.
What’s the best 404.php template you’ve seen come with a WordPress theme without modification?