GET. THIS. GAME. NOW
Also, one can now BUY all of their equipment (such as hats, weapons, etc.) through an in-game store. Basically, you can spend 2x the cost of Team Fortress 2 to get everything you want.
Now, I haven't even gotten into the gameplay yet. I have to say that this game is the most balanced multiplayer game I have every played. This isn't because of the weapons (although most default weapons are as powerful as the upgrade, but unlockable weapons may be better situationally), but because of how important teamwork is to succeed. Here's an example. As a medic, you can play a whole game without killing a person yourself, but in healing everyone you get points, and can easily end up at the top of the scoreboard by the end of a game.
Also, unlike games like COD, the people with better weapons have very slight advantages over you (once again, situationally.)
Over all, Team Fortress 2 has some of the deepest gameplay of any multiplayer shooter I have played, and also has beautiful visuals and a strong, nice player base. The learning curve may be a little steep for new players (9 classes to choose from may be overwhelming), but it is easily overcome because the game itself is lots of fun.
GET THIS GAME NOW