For those who would like to provide just that little bit of extra help for our users, Site Search could offer the option of auto-filling as users begin typing. This is particularly great if yow want to restrict the search freedom and make it easier for users to find content on your site, rather than being led to a 404 page. 

Take for example a holiday site with destinations to pick from in the search bar, or a medical conditions site where you start typing in the medical condition, or an FAQ page with a search bar that already shows you the corresponding page for the question you are asking. The search bar will pick up the letters in the page titles you have added to it and will auto-fill for the user.

There could also be an "others" option if they can't find what they are looking for.