What is the best online multiplayer game for PC?

[Yorick]

I'd recommend Team Fortress 2

[Heartofthedark]

For free games I can't really say, most games are pretty boring if they are free, as for paying games, I would have to say counter strike

[johndevid0987]

What is the best shotting online game for pc?
Convince me.
Oh,and i dont want to have to pay for anything but the internet my computer and the game itself