Want to make a delish chocolate fudge cake for my son's birthday. Need a great recipe....

This is a perennial 'best of' on Epicurious. The frosting will be fudgy or you can go for a candy bar effect with this spectacular chocolate Caramel ganache:
http://www.epicurious.com/recipes/food/views/Double-Chocolate-Layer-Cake-101275?id=101275

http://www.epicurious.com/recipes/food/views/Chocolate-Cake-with-Caramel-Milk-Chocolate-Frosting-107944

This is our go-to birthday cake. You can substitute water for the beer and/or coffee with equally yummy results! http://www.food52.com/recipes/3057_fudgy_chocolate_stout_cake

Here's the contest winner from Food52 along with one of the website creator's childhood favorites:
http://www.food52.com/recipes/2835_chocolate_bundt_cake
http://www.food52.com/blog/701_chocolate_dumpit_cake