Shoot the heads off all the mannequins within two minutes of beginning a game. Once done, go to the Nuketown population sign and press ACTION to play four classic Activision games.
You can kill the giant a number of ways but he can be resistant to some guns. Effective guns include the Acid gat, Death machine, Lsat (with headshots), or a LMG with the Deadshot Daiquiri perk doing headshots. These will usually kill him without wasting too much ammo.
