People have been asking for this so I decided to post this up.
This is for OFFLINE PROFILES ONLY. Halo Reach Credits and Unlock all Armor, Effects, and Max Rank GPD.
If you play on the modded account with another account who is an Xbox live member your rank will be Lt. Colonel Grade 3. If you play on your own or with another offline GT then your rank will be Inheritor. Tutorial on how to use GPD