It seems the Microsoft Store in the Westfield Century City Mall has been having some fun gaming events and launches with free stuff for a while now. Diablo 3's launch had some free stuff up for grabs I've heard.
Check the stores events calendar for future events.
Microsoft Store
10250 Santa Monica Blvd.
Los Angeles, CA 90067
Phone: 310-228-3550
Try Meetup's Microsoft Store Gaming Event Page