Very likely the best team-based first-person shooter currently on the market.
Bad Company 2 incorporates highly destructible environments, four-man squads as part of the overall team (as in real warfare), and realistic effects such as bullets taking time to reach their targets due to distance and bullet drop due to gravity (which makes sniping a bit difficult, but more skillful and tactical than that retarded quickscoping nonsense).
Set in the near future with an array of modern weaponry to choose from, players have access to four "kits," which include: Assault, Medic, Engineer, and Recon.
With very large maps and the option to engage in vehicular combat, players cannot adhere to a single style of play, whether they like it or not. Despite this reality, players still like to use the Medic kit because you don't have to reload as often with an LMG; and they still use the Recon kit because sniping doesn't require too much effort on their part.
Person 1: Hey! Do ya wanna play some MW2?
Person 2: Modern Warfail 2? Pssh! I'm gonna go play Battlefield Bad Company 2 where you need skill and teamwork in order to win.
Person 1: LOLWTFZOMGBBQ!?!!? CAMPERBITCHFUCKFACECAMPERHAXSIMPLEFACTCAMPERCAMPERCAMPERNOOBSCRUBALICOUSASDFASDFASDFASSDFASDFASDF