These are the confirmed multiplayer factions in Modern Warfare 2:
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Faction: Task Force 141
Task Force 141
A multinational grouping of military units or forces for the performance of a specific operation or assignment.
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Faction: US Army Rangers
US Army Rangers
A military Special Forces Unit of the United States Army. The Regiment is composed of rapidly-deployable light infantry forces with specialized skills that enable them to perform a variety of special operations missions.
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Faction: Op For
Op For
An opposing enemy force.
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Faction: Spetsnaz / Ultranationalists
Spetsnaz / Ultranationalists
Russian Army Special Forces, are the original Spetsnaz and are generally considered the best trained units of the Armed Forces of the Russian Federation.
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Unknown Faction
Unknown Faction
Not confirmed but it's high likely to be an rebellion faction in Rio de Janeiro.

These Modern Warfare 2 Multiplayer Game Modes have been confirmed as of now. Will be updated when more information is available.
Free-for-all

No Teams, everyone for himself. Kill everyone.
Confirmed here » in this video: AC-130 killstreak multiplayer »
Capture the Flag

Capture the enemies flag and return it to your teams base to score points.
Confirmed here » in this video: Uncut Multiplayer Video: Flag Runner »

i like your sig (last one)

Cool man, good post.