A very famous first-person shooting game!!
Counter-Strike is a simple team-based FPS (first-person shooter) in which opposing teams of Terrorists and Counter-Terrorists have to try and wipe each other out whilst managing map-specific objectives, like rescuing or protecting hostages and planting or defusing bombs. Each round is slightly more strategic than something like Capture The Flag though, because whenever you die you actually remain dead - until one team is wiped out completely, or until one team completes its objective.