How can I show selected items without exposed filters? I have a views which contains block and page view with exposed filter with my categories/taxonomy.

This is a beginner page for my users, so I just want to Show some items before they apply any filter. 
For this issue; I can add a checkbox to my content-type 'this is important'

Examples:
3 node added: 1,2,3. Node2 is important and needs to Show it without applying filters or like that. If a filter applyed, other node1 and 3 will be shown.

I'm using Drupal7 and latest version of Views, CCK etc.
Best regards.
Alternatively can you use "Promoted to front page" under "Publishing options" while adding content. This content will be the contents you need as important and will be visible to users.

Below that your view with exposed filter will be shown.
In View "Filter criteria" you can ADD "Content: Promoted to front page" option to show the non promoted contents, and also exposed filters. 

You can apply this logic in your content type also, if you need specific fields such as "Mark as Important", give it some Boolean value and select it in filter criteria as mentioned above. If not can be added from "Contextual filters".