This is kind of an odd tie-in for two Microsoft properties, but if you own both Perfect Dark on Xbox Live Arcade as well as the new Crackdown 2, then you may notice a new character available in Perfect Dark for multiplayer.
The secret character name is "Agent 4" and becomes available for Perfect Dark as soon as it detects a save file for Crackdown 2 on the Xbox 360 hard drive or on a memory unit such as a USB flash drive or memory card. The agent is only available as a skin for multiplayer though, and not as a single payer skin.
Odd, and a little offbeat, but if you own both games then why not I suppose. Crackdown 2 is available today in North America, and releases on European shores on July 9. There is also a demo of Crackdown 2 available for all to try out on the Xbox Live Marketplace now.