It is never easy to determine which deal is the best these days. So here is a link to a post that discusses all the various GoDaddy coupons for domain name discounts. As it turns out it depends on how many domain names you want to purchase. Here are the deals, an image showing the discounts and a video as well.
Coupon Code: 99coms (use this link)
Deal: 1 domain at $.99 and each additional domain is $9.99
Coupon Code: 249sale (use this link)
Deal: 1 domain at $2.49 and each additional domain is $9.99
Coupon Code: 495coms (use this link)
Deal: up to 3 domains at $4.95 and each additional domain is $7.99
Coupon Code: 599coms (use this link)
Deal: 3 domains at $5.99 and each additional domain is $9.99
Coupon Code: fan3 (use this link)
Deal: 3 domains at $7.49 and each additional domain is $7.99

It's me - Tyna! I am the edit-tor as they say. Now you found me, so follow me ;-)