The Air Support Marker is featured in Call of Duty: Modern Warfare 2's Multiplayer to signal locations for airdrop killstreaks. Player should be advised that it takes a bit of time for the drop to actually reach the player, so it is best to call it in somewhere far from the combat.
The Air Support Marker returns in Call of Duty: Black Ops, and is featured in the campaign mission "Project Nova", where it marks locations for friendly mortar strikes. It differs from the multiplayer version in that it takes the appearance of a Willy Pete grenade, and uses the tactical grenade slot instead of being brought out first.
The Air Support Marker returns and is once again used to mark locations for friendly airdrops. The marker seems a bit clunkier in this game, as it does not bounce as much when thrown, and also doesn't seem to go as far as its Modern Warfare 2 counterpart. It also makes a bit more noise when thrown than its Modern Warfare counterparts.
This grenade is featured in the missions "Bag and Drag", "Iron Lady", and "Down the Rabbit Hole". It's main purpose is to signal locations from AI-controlled airstrikes, typically from an AC-130. However, in "Iron Lady", it is also used to signal a bombing run that eventually destroys the Eiffel Tower. It emits a purple smoke to mark the location.
The Air Support Marker returns yet again in Call of Duty: Modern Warfare 3, and is available for marking locations in for airdrops in Multiplayer. The physics of the marker is much similar to the Call of Duty: Modern Warfare 2 variant.
The Air Support Marker is also featured in the Special Ops mission Toxic Paradise. It functions exactly the same as it does in the campaign. However, the Air Support Marker is also used by enemies, in which it emits red smoke, instead of the normal purple on where the strike will be placed.
The Air Support Marker is also available in Survival Mode, where it marks the location for a friendly AC-130 strike. It costs $2500 and is available from the Air Support Armory at level 4. The marker is sticky, so you can stick it to an enemy little bird to destroy it. It is also possible to stick it to an Mi-8 while it is dropping a juggernaut, but it will not destroy it.