Microsoft Store. The offer is valid on up to three games. Everyone who pre-orders a game via the Microsoft Store website gets $10 for the Store or Xbox Live, meaning Rewards members are getting a $5 bump.
"So order Call of Duty: Advanced Warfare for yourself and Lego Batman 3: Beyond Gotham as a holiday gift, and get 30,000 credits to redeem on games, map packs, season passes, movies, TV shows and more," Microsoft writes on Xbox Wire. "Xbox Live Rewards members will receive 15,000 rewards credits, 5,000 credits more than non-Rewards members receive, for each game pre-ordered on both Xbox One and Xbox 360."
Microsoft re-launched its Xbox Live Rewards program last year after phasing out Microsoft Points in favor of real-world, local currencies.