Halo: The Master Chief Collection received a large patch today, fixing numerous issues with the game which has seen its shared of bugs since launch last November. You'll also find a new multiplayer map, over 100 new achievements to earn, and several tweaks for co-op players to provide a more stable experience.
Perhaps the biggest "fix" though is the addition of Halo 3: ODST, the entire game, available to download for free for those that purchased the game before December 19th, 2014. If you didn't purchase the game then, the content is just $4.99 to download.
Sadly ODST's best feature, the co-op Firefight Mode, is not included.
Here's the full list of patch fixes.
NEW FEATURES AND CONTENT Remnant [Remake of the Halo 2 Classic multiplayer map Relic] is now available for all users 100 New Achievements added for ODST and Remnant. To see the list, head here. Players can now search for Gamertags and access file share, by selecting their own Gamertag in the Active Roster. To learn how, head here. Enables DLC addition of Halo 3: ODST campaign (available separately via the Xbox Store). For more information on Halo 3: ODST campaign, go here. RANKING Improved skill matchmaking for parties in ranked playlists Made an updated to ensure that parties are no longer separated onto different teams in ranked playlists Improved rank stability to prevent ranks from incorrectly resetting QUIT AND LOSS PENALTIES Quit and loss penalties are now applied immediately in matchmaking HALO: CE Resolved Assault Rifle and Shotgun registration issues Fixed an issue with vehicle audio in split-screen Reduced occurrences of players falling out of map Improved stability while title is in “suspend” mode Improved music playback for Campaign HALO 2 CLASSIC Fixed an issue where playlist scores posted to Leaderboards incorrectly Improved host migration handling in for peer-to-peer custom game matches HALO 3 Added UI support for Halo 3 voice chat in matchmaking Improved Campaign stability Fixed an issue where the scoring HUD would not display in Campaign Fixed an issue where some players could experience a delayed spawn into a matchmade game HALO 4 Fixed an issue where the scoring HUD would not display in Campaign PARTIES & ROSTER Added support for displaying parties as a group in the roster Improved handling of dedicated servers Team colors are preserved after every match in custom games Fixed a host migration issue for Custom Games Improved handling of player joinability and leader promotions through Active Roster Improved stability of 16 player parties FORGE Improved Forge Stability with large number of players on high budget maps Added support for Infection within Halo 3 Forge maps Fixed an issue where “Place at Start” did not function correctly in Halo 3 Fixed an issue where controller settings were not respected in Halo 2: Anniversary ACHIEVEMENTS Improvements to achievement unlocking throughout title Fixed an issue that prevented the Blast Can achievements from unlocking in matchmaking UI, STABILITY, & MISC Made improvements to stat tracking for all titles Improved functionality of unlock notifications Improved voice chat functionality throughout all titles Improved PGCR stats/details and stat uploading reliability Fixed issues where local & shared files may not appear under “My Files” Improved Stability of Co-op play in Campaign Playlists UI now sorts achievements, nameplates, and avatars based on what you have unlocked Improved Scoring functionality during Co-Op Campaign sessions Improved Spartan Ops performance Improvements made to mission progression in Campaign Playlists Improved Rival functionality in Campaign Playlists Improved stability for Halo 2: Anniversary map loading in matchmaking Final scoreboard is now displayed during outro loading screen after a match