Like Capture the Flag, this mod needs no introduction. However, for the uninitiated, Counter-Strike began as a modification for Half-Life by Minh "Gooseman" Le and Jess "Cliffe" Cliffe. It's the classic team versus team multiplayer environment, where one team serves as the terrorists and the other serves as the counter-terrorists. Each round is completed by either meeting the mission objective or by eliminating the opposing team. Players earn virtual money by winning a round, killing an enemy, planting a bomb, and so on. The money is then used to purchase equipment needed within the round--surviving players can retain their equipment for use in the next round. Counter-Strike quickly amassed a huge following and attracted hardcore professional gamers.
The mod was eventually expanded into a separate, full game, while retaining the Half-Life engine. The retail version came bundled with Team Fortress Classic, Opposing Force, and the Wanted, Redemption, and Firearms mods. Counter-Strike: Condition Zero followed in 2004, containing a single-player campaign, bots, and other changes. Counter-Strike: Source is the current edition of the franchise, using Valve's Source engine developed for Half-Life 2.