I think we should have a sticky thread about it. I search for Godaddy promo codes everyday to renew domains and I'm sure there are plenty of people here who do the same. It would be lot easy to everyone if we can share what we find.
Here's the latest 1 USD Godaddy promo code
BIGGAME1
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bid395a - 3 new .com's at $3.95
gtnftu03 - 3 new .com's at $3.95
gdbbe1026 - 30% off
gdx138b - 25% off
SAVE25Y - 25% off ( best one for CO. renewals)