Go, Chief! Gun It!
From Halopedia, the Halo wiki
Go, Chief! Gun It!
Go, Chief! Gun It! is an achievement in Halo: The Master Chief Collection. It is unlocked by beating the 20 minute par time on the level Halo. The achievement is worth 10 Gamerpoints and can be unlocked on any difficulty.
Trivia
The name of the achievement is a reference to Cortana's final line of dialogue during gameplay in the level.