Camper.
No way bro. Believe it or not, but aggressive play rules the day in FPS's.
It goes against logic. If everone else is hiding in their cubby holes, and im running around, youd think Id get blasted in the back right? Somehow no. I wind up just torching guys left and right.
Go on youtube and watch any one of the millions of Youtube vids of guys playing COD (or any FPS). Are they camping? No, they are constantly moving throughout the entire game and end with scores of 66-0.
So from one grand master of FPS's to a padawan, my 1 piece of advice is to get aggressive. Get into the enemies base ASAP and just start racking up kills. Never, Ever stop moving. Its both superfun, and once you get the hang of it, youll be better than 99% of the people you come across.
* Not to mention, constantly moving makes you learn every map like the back of your hand. I havent played COD4 in more than 2 years and I can perfectly detail every piece of every map.