Bungie is a company that hardly needs any more exposure on Xbox Live, and Avatar clothing is something that hardly needs to be purchased by anyone, but exceptions can be made for good causes!
In honor of the developer's 20th anniversary, it's made new Bungie logo t-shirts available on the Avatar Marketplace for both male and female avatars. The proceeds from the 80 Microsoft Point ($1) purchase go to "charity" -- none is specified, but we would assume it's Bungie's own Foundation, which gives pre-loaded iPads to children's hospitals.
If you'd like to interact with Bungie in a more violent manner, the team is playing Halo: Reach all day (it's "Bungie Day") and giving away steaks.
[Thanks, David from Berkeley]