A person who fully believes that they have the skill and cunning of popular American Cinema icon "Rambo", but is in fact only a walking parody of the character.
Whereas Rambo takes to the front lines and mows enemies down while never getting hit himself, a "Ramjoe" goes in guns-blazing, only to feed kills to the opposing team and earn a poor Kill Death Ratio.
Person 1: All you're doing is camping with that stupid sniper rifle, get down here and shank people like a man.
Person 2: Stop Ramjoe-ing dude, you've died like 40 times.
*Person 3 runs by with a bouncing betty*