Double EXP Weekend
Every weekend, from Thursday at 12:00pm(est) to Monday 12:00pm(est) (North American Timezone), a playlist called the Double EXP Weekend opens for Halo 3 players with gametypes that aren't normally available for other matches on usual weekdays. Each win gives 2 EXP points, but losses will still not take away EXP (However, if you quit out in a game, the standard EXP penalty will be applied). Most of these playlists are unranked, except for the Legendary Brawl playlist, the Living Dead playlist, and the Valentine's Day Massacre playlist. By far, the most featured playlist is the Grifball playlist, including slightly different arenas, and different leagues (Spring leagues, summer leagues etc.) Team SWAT changed into a permanent gametype in the Hardcore playlist as of May 2008, and Team Snipers as of November 2008.
In Halo: Reach, so far the closest equivalent to Double EXP are the weekend credit Super Jackpots that appear on specific playlists.
Double EXP Weekend Playlists
For certain Holidays, such as Halloween, Valentine's Day, and Fourth of July, playlists were devoted to the day with special gametypes and maps.
Coming Double EXP Weekends
Double EXP weekends were dated to end on September 13, the day before the release of Halo: Reach. However, as of October 2010, double EXP playlists are still made available every weekend.