Rebuild menu cache to force recognition of menus added while developing a module
Rebuild menus so that menu items and callbacks defined through the menu system take effect while you are developing a module.
The quick fix:
I know I posted about this before, and it took me five minutes to find.
Anyhow, this is useful during development to clear and rebuild the menu cache, so that your menus added to a module (hook_menu) actually will show up for you, without reinstalling the module or something stupid.
Then immediately remove your call to menu_rebuild!
Actually I got a 500 Internal server error. But it worked.