Call of Duty: Modern Warfare has been available to pre-order on Steam for a few weeks now, but if you pre-order now, you'll also get a free copy of the superb Call of Duty 4: Modern Warfare.
CoD 4 was Infinity Ward's first attempt to bring the intensity of Call of Duty's linear campaigns to a near-future setting, and it worked beautifully. The campaign retained the grim realism of the earlier entries in the series without succumbing to the bombastic action movie set pieces of Modern Warfare 2 and Call of Duty: Black Ops. Missions like All Ghillied Up show Call of Duty at its most restrained and atmospheric. There's a sturdy multiplayer component, too. Corsair's $10,000 CoD 4 tournament is set to kick off next month.
If you do opt for the Modern Warfare 3 pre-order , you'll get a copy of Call of Duty 4 straight away. If you already own it, you can gift it to a friend.