Join another player's game.

Complete act IV.

Kill 250 zombies using firearms.

Use a large medkit to heal an injury of 5% or less.

Loot 5 Exceptional Weapons.

Complete act II.

Kill 5 Infected in a row with a single blow.

Find 60 collectibles.

Reach level 25.

Kill 250 zombies with modified weapons.

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

Kill 25 zombies with your bare fists.

Kill a Suicider with a grenade.