Back in my high school days, my friend and I would take turns playing co-op X-COM. I would take care of the business and administration side as well as interception of alien craft. Once we hit the ground though, it was his territory. I was very vocal in my advisement during these missions and he was quite frank in making requests for research and supply. Overall it made a non-co-op game one of my favorite co-op titles of all time.