This weekend Activision and Infinity Ward are launching the 'Game for Good' event, encouraging gamers to play Modern Warfare 2 to raise money for the War Child charity.
The initiative is being organised with the help of GAME and Xbox Live and all you have to do to take part is play Call of Duty: Modern Warfare 2 online on the 5th and 6th of December (that's this weekend).
If more than 600,000 UK users get their Modern Warfare on, the War Child charity will receive a donation of £150,000, says Activision. An extra £25,000 will be donated for every 100,000 users after that, up to a maximum total of £250,000.
For more information and to show your support visit the Game for Good Facebook page.
[Update] Microsoft has clarified its support for the weekend, saying that Xbox Live Gold will not be free, but Silver members can take part by playing Special Ops mode.