It's hard to define Chief and Cortana's relationship, but there's definitely something Freudian about it - Cortana was created from a flash clone of Doctor Catherine Halsey, who was also in charge of the SPARTAN-II program, taking on a distorted mother role to Spartans such as John-117.
Anyway, I had a lot of fun with Grifball and the Flood game mode of Halo 4 when I was 14.