I don't usually have any GoDaddy promo code on hand, so I usually search for some. Usually I don't find any that work. Except this time I search and found one that works, so I think I'll share it.
OYH3 - $2 Off / $6.95 any .COM
I just used the above code on registering a new domain and renewing an existing one, and it was applied to both.