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.
Its Counter-Strike, what else can i say?
Aside from having fairly unbalanced AS maps and CS maps, CS 1.6 will always be better than CS:S. Despite lacking in visuals, CS 1.6 makes up by having smoother game play, more up-beat/perky levels, and in general, more levels.
Its very balanced, its very fun, and still doing okay in 2011, despite being over 10 years old.