Halo is a first person shooter. It is only on the Xbox for consoles but is coming out for PC soon.
Most people who have played it consider it the best game ever.  The single player is brilliant, but the multiplayer is where the most fun is.  People can play 2 player cooperative, 2-4 player split screen, link 4 xboxes together with 1-4 player on each xbox for a total of 16 players.  Another thing that makes Halo so great is the vehicles, the driving is better than most racing games. 

 

Multiplayer:

-2 to 4 player split screen

-up to 4 xboxes with 1-4 on each xbox over lan to make up to16 total players

-2 player cooperative play

Gametypes

-Death Match (team or free for all)

-Capture the Flag (team or free for all)

-Oddball (team or free for all)

-King of the Hill (team or free for all)

-Race (team or free for all)

-You can make your own game types, and edit any gametype