They often offer "Rockstar" or "Steam" keys at a discount.
For , there is no single "top" license key code; rather, license keys are unique alphanumeric strings issued upon purchase through official retailers to validate your copy. If you are looking for cheat codes to enhance your gameplay, those are universal and can be entered at any time. Purchasing Official License Keys
The 16-20 character activation code is typically located on the back of the game's manual/booklet inside the box. Legacy Steam Version: