Urban Mercenary

Urban Mercenary was one of the first multiplayer games where you could get real money in online tournaments. The game allowed players to bet and split the money among the winners and earn actual money for fragging online. The game used GLQuake - modification of Quake Engine and was available for free downloading on developer's website. However, the servers of the game are offline for several years and developer's website is dead, so now the game is abandonware. Game has bots so you can play it offline.