Complete the "Handicapable" level

Kill 75 enemies with headshots

Complete the "It's All Greek To Me" level

Perform a multi-kill with a melee weapon

Switch between Brian and Stewie 10 times in Story Mode

Successfully kill an enemy with one shot

Get 30 kills with the Magnum secondary fire in the single player Campaign.

Get 30 headshots while scoped in with the Fareye or Marksman in the single player Campaign.

Defeat the Goliath in the single player Campaign.

Win 100 multiplayer games.

Incinerate 500 enemies

Beat the Challenge of the Gods