Create Controller file catalog\controller\productallproduct.php and paste below code http://pastebin.com/jZq3hZyc
Create View file catalog\view\theme\default\template\productallproduct.tpl and paste below code http://pastebin.com/1HNh3x734 . Create Language file catalog\language\en-gb\product\allproduct.php and paste below code http://pastebin.com/EcyJH7F9
Enable module from back-end You can see link in menu
Display All Category in Menu
Open and edit your category:
Select tab Data:
Find and Check:Top: Display in the top menu bar. Note : Only works for the top parent categories.You will need to check all the top level categories.It’s Opencart bugs.