Like Peanut Butter and Chocolate
From Halopedia, the Halo wiki
Like Peanut Butter and Chocolate is an achievement in Halo: The Master Chief Collection. It is unlocked by completing any level of Halo 2: Anniversary co-op on Heroic or Legendary, with the Masterblaster skull active. The Masterblaster skull causes one player's shields recharge to overshield level but that player can only melee, while the second player has no shields but infinite ammo; the roles switch after a number of enemy kills. The achievement is worth 10 Gamerscore.
The name of the achievement refers to two things which complement each other particularly well.