Play the world's number 1 online action game. Engage in an incredibly realistic brand of terrorist warfare in this wildly popular team-based game. Ally with teammates to complete strategic missions. Take out enemy sites. Rescue hostages. Your role affects your team's success. Your team's success affects your role.
Counter-Strike is a game by Valve for Windows. It is better than TFC, but was originally was a modification for Half-Life. It's really good and is a great example of the phrase, "Team-Based".