Cause the Basilisk to retreat

Defeated Zed.

Pick up 1,000 zombie medals.

Buy a combo at Chop2Shop.Zom and use it.

Complete "Ballistic Trauma" in Story Mode

Kill 150 enemies with melee.

Escape the Polar Sea.

Get 10 critters on screen at once.

Kill eight enemies in eight seconds using the Darkstar Fission Tether with two or more teammates.

Complete Terawatt Forest.

Kill 500 enemies.

Defeat the Wigwump.

Buy half of the weapons.