Survive 15 consecutive waves with each of the 4 characters.

Sever 100 limbs.

Kill 250 zombies using firearms.

Survive wave 30.

Reach level 25.

Survive 5 waves using only your fists and legs.

Use a hammer to kill a series of 15 zombies without taking damage.

Save 5 people besieged by zombies.

Play with 10 different co-op partners for at least 15 minutes each.

Kill 50 zombies using a vehicle.

Create a customized weapon.

Complete 5 quests in a single co-op game with the same partners.

Play in a co-op team of 4 different playable characters.