halo 3: odst
A spinoff title in the Halo franchise. Set during the events of Halo 2, the game follows a squad of ODSTs dropped into the city of New Mombasa to fight the Covenant invasion.
ODST only featured the campaign and Firefight (a new PvE horde mode that would later be a mainstay in the franchise), and was bundled with a separate disk that contained the multiplayer portion of Halo 3 with all of the post-release DLC instead of a dedicated PvP multiplayer mode.
This tag implicates halo_(series) (learn more).