One of the advantages of offering a game for sale in downloadable form through Steam is the fact you can make it free-to-play for short periods of time. It pretty much guarantees a much larger set of gamers will at least try your game, and at the end of the free play time they may actually buy it.Activision is taking advantage of Steam’s free-to-play option this weekend by making the Call of Duty: Black Ops 2 multiplayer portion free-to-play. From now until 1pm PT on Sunday February 24, you can download and play online completely free of charge. And to sweeten the deal, if by Sunday you want to buy the game to carry on playing, Steam is offering you 33 percent off.The reason for the free promotion is due to Treyarch and Activision launching the first DLC for the game next week on February 28. Clearly they want to boost player numbers in time to purchase that extra content.The DLC pack is called Revolution and will be made available for both PC and PS3. It will offer four new multiplayer maps (Hydro, Grind, Downhill, and Mirage), a new weapon, a new Zombies map (Die Rise), and a new Zombies game mode. The new weapon is called the Peacekeeper and brings together “the mobility of a SMG with the range of an Assault Rifle.” Finally, the new Zombies game mode is called Turned and lets players fight each other in zombie form.If Black Ops 2 isn’t your thing, Steam is also offering a free play weekend for the strategy simulation game Gratuitous Space Battles. And if you like it, you can purchase the full game or the Complete Pack for 75 percent off.