BZFlag is a multiplayer 3D tank game commonly found on SGI Irix systems (a crappy Windows version is also now available). A large number of people can play BZFlag at the same time. I am not sure of the exact amount, but it has always been "enough". When playing the game, you are in control of a tank in a 3D arena, with buildings, pyramids and other obstacles. The point of the game is to stay alive, to keep from getting shot by the other players. Players can join as color coded teams, or join as part of the rogue team (every (wo)man for themselves)
To make this more exciting, the tanks are able to jump, either into the air or on top of buildings. Planted throughout the game board are various BZFlags: white flags which can either harm you or give you special powers. Each tank can only hold one flag at a time and one cannot tell what a flag is before picking it up. "Bad" flags include blindness, radar jamming, obesity (you become a huge target), left or right turn only, momentum (can't stop moving). Bad flags stay with the player for a set amount of time before dropping, good flags can be dropped by the player at any time. Bad flags can be negated by picking up a yellow restoration flag. "Good" flags include stealth (you don't show up on radar), cloaking (invisibility), rapid fire, machine gun, high speed, tiny (makes your tank tiny), narrow (you become very hard to hit from head on), shield, identify (allows you to see what other flags are before you pick them up), oscillation overthruster (allows you to move through obstacles), shock wave (destroys any other tanks within a certain radius), ricochet, super bullet (allows you to shoot through walls and at longer distances), guided missile and laser.
The very best flag is (IMHO) the laser flag. Laser allows you to shoot anyone else from as far away as you like (normal ammo has a limited range). If you can grab the laser flag and get into a corner with it, the rest of the players will have to work together very hard to displace you, while you sit back and rack up a high score. Laser does have one not-so-well-known weakness though: it cannot shoot a player that has cloaking.
Many of the other flags have certain small weaknesses or special uses that are secondary to their primary functions.
The default (and in my experience, most commonly used) board settings include only buildings and pyramids (the game is usually better with the bad flags option turned off, as well). Other board configurations include full time ricochet (dangerous in combination with the infinitly reflecting laser) and/or teleporters. These options are best used to spice up a 2 or 3 player game.
A super procrastination tool, BZFlag has been solely responsible for a great many Comparitive Programming Languages or Software Engineering projects being turned in late, as well as a few failed Stats quizzes and missed Art History or Mass Comm classes. Or so I have heard ; )
almost forgot the BZFlag home page:
the source code to the game is available for anyone interested in 3D game programming