Break On Through is a 4 four-player co-op shooter that takes Halo(when it was good), TIMEZONE, Gears of War, and Call of Duty(when it was also good) and mashes it into a 2-way world. In this game, the Halo Universe collides with TIMEZONE after a Covenant Slipspace Jump fails horribly, creating a rift in the fabric of reality. Spartans fight alongside Loners, SCD, and our protagonists as the Covenant scrambles to eliminate humanity on both sides of the rift, their job is now a lot harder thanks to said rift.
You first play as John 117(Chief), and end as Flynn. The game lasts 3 weeks straight, and that's in speedrun mode. You fight and fight and fight through hordes of Covenant Troops, survive planets being glassed, and ultimately beat back the Covenant through Guerrilla Tactics in the TIMEZONE world, and by literally glassing the Covenant Homeworld in the HALO world. Ultimately, after the Covenant are beaten back and obliterated, you part ways with the UNSC, or, if you wish, choose to join them.
...And let's just say the Red Kobra are obliterated.