In Google Search, or in the Chrome Omnibox, suggestions are great. You only have to type a couple of letters and the site, app, bookmark, you're looking for is suggested. The feature is great, when it works, but it doesn't always work as you'd want it.
And when it fails it's annoying, especially since it actually makes it harder to get to the thing you want to get to, by suggesting something else.
Thankfully, there's a way of dealing with annoying suggestions, one that's not very obvious, you can actually remove suggestions from the Omnibox via a keyboard shortcut.
Just select the suggestion you want gone with your arrow keys and then press Shift+Delete, or Shift+Fn+Delete on Mac, and that's it. Note that this only works for search suggestions and history items, not bookmarks or apps.
Also note that the changes aren't always persistent and that the items may eventually resurface if you use them again several times, that's just how the algorithm works.