Counter Strike: Source is a game that'll give you your head shot fix.
It's a pretty simple game that'll keep you hooked for hours a day and provides the satisfying feeling of fragging your enemy. It takes practice to get as good as most players are these days because the game has been around since half life one when they released just plain counter strike. But those veteran players aren't really seen around as much as they used to be and they usually stick to their roots at counter strike 1.6 and don't much want to venture onto the source engine.
Counter Strike: Source is a great game that's pretty much for anyone wants to kill a couple hours or to someone that wants to compete professionally, this game is for everyone which makes it so diverse and a fun game to play.