If you want to be part of an attempt to break the world record for most participants in a first-person shootout, mark January 29th down on your calendar. MuchDifferent, a Swedish nonprofit dedicated to "development of over-the-top technology," will host a game of "Man vs. Machine" with the hopes of having 1,000 players participate. Eight single-threaded servers running Unity (the in-browser game engine and development platform powering this game) will handle this potentially massive traffic influx. Each server will load up a portion of the battlefield and all servers are linked together through PikkoServer, a dynamic load balancer and traffic router that will help keep the game from lagging out or crashing due to the massive number of participants.
As for the actual game experience, it sounds like it'll be a pretty basic "kill or be killed" scenario with two teams you can join when registering: the aforementioned men and machines. It's a one-time-only match, and you'll need to register and buy a ticket ahead of time if you want to get in. There's a small fee, but all money collected is being donated to Engineers Without Borders, so there's no profit changing hands here. MuchDifferent claims the largest commercial FPS server is PlanetSide, which hosts a max of 399 players — so even if only half of the maximum capacity shows up for "Man vs. Machine," the world record should be in the bag.