Quickly one.
Today I was tasked to remove node from search results on our side.
It looks like easy but it is not if you are using basic Drupal 7 search engine.
Options are:

1. remove items from search tables (but they will be re-populated with next cron run)
2. build module with query alter hook (to much work for simple thing like this)
3. alter search-result.tpl.php template.

And 3rd one is one that I used. Since site already have inside custom templates folder search-result.tpl.php
I just added at the top:

if ($result["node"]->nid == <excluded nid>) {  
      // search result alter  
}  
else {  
    // everything else  
}  

and it is done.
Note to myself: next time use Search API and assign views to the search. Then I  use Views to override search results (including all its features: filtering, sorting, etc.
Create a custom field such as “Exclude this node from search,” and set the filter to exclude nodes with that field or/and certain content types.