Overriding menu items and links

Hi guys,
I wanted to know how we could override the menu items and links of any module. In my case I want to disable some menu items and links(developed by implementing hook_user) without making changes in these modules.
How can I override them using my modules.
Now if I define the same menu item(path) in my module as non cached menu item and use a callback to a drupal page not found, then it works. But it will definitely use some extra effort. So I don't want to override them by defining them in non caching menus. Again if I override them in caching menus in my module then there is no guarantee that my path will override the other ones.
So could anyone please guide me on this.
Seeking for help