If you don't want a small, amusing detail in Grand Theft Auto IV spoiled, stop reading! There are minor spoilers ahead!
Now that we've cleared the room, here's a little GTA humor, fresh from Liberty City's TV station. On the "show" Republican Space Rangers, note the costumes of the rangers. They're fully decked out in Master Chief's armor.
Here's a youtube link...but you should really check it out in-game!