I Need a Weapon is a campaign achievement in Halo: Reach. This achievement is obtained when a player completes Nightfall on Normal difficulty or higher. It is represented by an icon of the planet Reach, over which is imposed the Roman numeral for four. It is also a phrase used by Master Chief in the opening cutscene of Halo 2. When the Covenant attack the ship that he is on, he is told ro defend the station. He replies with a "Yes sir," turns to Sargent Johnson and says "I need a weapon." Using this meme after a picture implies that Master Chief wants to kill the person in the previous picture, hence the reason he needs a weapon.