From Halopedia, the Halo wiki
Sci-fi, steampunk, Halo novels (no shock) Halo (Obviously), Gears of War, Battlefield
The first sight of the Forerunner structures in Halo 4 (the beginning of the level "Requiem")
First game of Halo 3; "owned" doesn't even begin to cover it.
I've played the series since before it came out (thank you uncle at Microsoft).