
Spartan 085
You don't need to have an online account in order to gain achievements. Any achievements you unlock while offline on your gamertag will stay with you no matter what. However, with the new map packs that Bungie has released, you'll need to be signed into Xbox Live in order to have the updates installed onto you Xbox 360 hard drive. After those updates are placed onto your hard drive, you'll be able to gain those achievements as well.
The multiplayer achievements are a different story, you need to be signed into Xbox Live with your gamertag in order to play any ranked matches. I believe as a guest you can still play Social matches but that's as far as you're extent will go because you still need to have an online account to unlock achievements. No achievements will be awarded to guest accounts.
Added Oct 22 2009
ID: 322140
Current Rating:
Not Rated