Today on Xbox Live Arcade you can get your hands on Warlords and Buku Sudoku,  each game will set you back 800 MS Points.

Warlords is one of the classic multiplayer experiences of the coin-op era. You and three other players (A.I. controlled or Human), join together in a Breakout-style battle, each controlling a paddle protecting their own castle from rebounding fireballs. Use your skill to deflect these missiles onto other players’ castles. Once you breach each opponent’s walls, it’s game over for them, until the last man standing wins the day!

Buku Sudoku lets you play cooperatively with friends, race head-to-head to complete a puzzle first, you can even try the new battle mode in which completing a line, row, or square will remove numbers from your opponent’s board!

Thanks to the Major for the info.