UT99 is a true classic and despite its age, it's better than many newer first-person shooters out there.
The technology that powers Unreal Tournament was impressive in 1999, probably the most advanced on the gaming scene at that time. The Unreal Engine gave level designers the possibility to create breathtaking environments. Indoor, outdoor, you name it, Unreal Tournament has it all. You will get the chance to do battle in a variety of locales like space stations, floating asteroids, exotic beaches, islands surrounded by lava and even underwater.
If you thought that was impressive, wait till you try playing (either single-player or multi-player, the differences are not very big thanks to the brilliant bot AI). You can play the classic Deathmatch or Capture the Flag plus Domination and Assault. There's a wide range of weapons to choose from (snipers, medium range, close range and even small nuclear devices) and a few power-ups to compensate for the huge fire-power. It's all perfectly balanced, very straight-forward and manages to feels unique and fun every time, online or off.
UT99 also gives users the chance to make their own arenas of combat via Unreal Editor, which comes with the game. It's a powerful tool for editing, combine this with a few other programs and you can do just about anything (from arenas to mutators and other mods). This gives the game extra reply value.
Needless to say, Unreal Tournament simply is one of the best shooters ever so go buy it if you haven't done that yet.