Stargate Atlantis/Generation Kill crossover, where sergeant Brad Colbert joins a Gate team on Atlantis, and it's not just the space vampires he has to adjust to.
With an ensemble cast of canon characters from both fandoms, plus original characters
AKA You want to recruit me for WHAT? Daily life on Atlantis, Outsider point of view, Sgt Brad Colbert has adventures IN SPACE
Gen/maybe a little Het down the line, but not central to the story
Currently up to chapter 14 of manylots and putting out about a chapter a week
Warnings: marines in space - lots of swearing.Find it here