Chrome's omnibox can be a little too helpful sometimes. Begin entering in a word or phrase, and it starts autocompleting, spitting out suggested search terms, e-mails, bookmarks, and past pages from your browser history.
In many instances, however, you use the omnibox to perform a simple Web search and want to see only suggested search terms. In such an instance, enter a question mark before your search term and in the omnibox's drop-down menu, you'll see only search suggestions.
Now, you can simply click in the omnibox and key in a "?" or you can use a keyboard shortcut to enter the question mark in the omnibox, saving you from having to click first. For Windows, use Ctrl-K or Ctrl-E. For Mac, use ?-Option-F.