I have seen all of these in production code:

Example 1: 

throw new NullReferenceException();

Example 2:

public class AbstractController : Controller
// or 
// public class AbstractPag : Page
{
    public static bool IsAdmin { get;set; }
}

Example 3:

public static class BlogMgr
{
    public static void AddPostToBlog(Blog blog, Post post)
    {
            blog.Posts.Add(post);
            post.Blog = blog;
    }
}

* I could only think of three, but I didn't want to modify the title.  Can you complete the list?