Is there a chance to delete Work Item from TFS, or all I can do is just to rename it.
Update: This question was for TFS 2008. New version (2010) have out of the
If you want to do this without using the tool suggested in the accepted answer, here is a quick summary of what to do. This is based on the corresponding MSDN article suggested in another answer.
Using the start menu:
Determine the team project collection URL. An example is http://ServerName:Port/VirtualDirectoryName/CollectionName.
Determine the work item id.
Invoke the following command, substituting the two above values:
witadmin destroywi /collection:CollectionURL /id:id
See the MSDN article for more details. Note that you need permission for this to work.