That should be the closing shot of the game - Master Chief's helmet visor slides back and you finally get to see his face. A tear is rolling down his cheek because he had to kill Cortana, his forbidden love. Forbidden because A) She was a hologram, and B) They castrate the Spartans so they aren't distracted from the killing by wanting to fuck all the alien chicks they have to kill. Anyway, he's crying over Cortana, and then you see him stick the Slurpee Straw in his mouth. It's a Game Fuel Slurpee. The scene fades to the sounds of Master Chief sucking up his Slurpee, and the credits roll.