The very first Xbox game that I bought with Live support was Rainbow Six.  It was an amazingly fun game to play online and off line.  This is how I met most of my original friends on Xbox Live and how I first got addicted to online first person shooters.  Tomorrow is the release of Rainbow Six Vegas 2 and I will be buying a copy of the game after work.

Rainbow Six is probably one of the best balances of a fun tactical shooter single player game and a stealthy precision based FPS online.  Since Rainbow Six tends to aim to be as close as possible to realistic it does not take much to get killed or get kills online.  Obviously there are some people that never stopped playing the last version of the game so they will be tough as nails to play against.  Thankfully there is true skill and RSV2 should have it's own ranking system to help keep the matches balanced.

The early reviews of this game have been very favorable so I think it's safe to say the Rainbow Six brand is still in good shape.  The folks that built this game are some of the best in the industry.  If you want a tough but fun online experience be sure to check this one out.