name.com is running a $5.99 offer for new domain registrations. That would be the cheapest offer I guess.
You can try Name.com Each new domain registration for $5.99 Mydomain.com Each new domain registration for $7.39 with coupon code "htmli.info" dynadot.com Each new domain registration at only $8.99, and you can delete your domain within 5days if you want.
For Godaddy I'll suggest you to get a coupon code before you register a domain. You can search they coupon code at Google or check my signature.
I prefer 1and1, since you get free private registration (you may with others as well, I know GoDaddy does it for free only on bulk orders).