For those of you who don't already own Call of Duty: Black Ops, Activision is holding a free weekend event on Steam from September 1st-4th. During this event, you can download and play the entire multiplayer portion of the game free of charge. They're also offering a 50% discount on select Call of Duty titles, along with a 33% discount on Call of Duty: Black Ops from now until 10AM PST on Monday, September 5th. So if you enjoy your time with the free trial, be sure to grab the full game while it's cheap! :)