No damage
Not unlocked yetComplete a level without incurring any damage
Max
Not unlocked yetMax out any upgrade on any character
Max Max
Not unlocked yetMax out all 4 upgrades on any one character
Firing on all cyclinders
Not unlocked yetUnlock all 5 weapons
Policeman
Not unlocked yetUnlock Policeman character
Sheriff
Not unlocked yetUnlock Sheriff character
Samurai
Not unlocked yetUnlock Samurai character
Special Agent
Not unlocked yetUnlock Agent character
Junior Protector
Not unlocked yetComplete any 10 missions
Run for your life!
Not unlocked yetComplete 5 Run For Your Life missions
Protect the street!
Not unlocked yetComplete 5 Protect The Street missions
Collect coins!
Not unlocked yetComplete 5 Collect Coins missions
Stay alive!
Not unlocked yetComplete 5 Stay Alive missions
Kill the zombie boss!
Not unlocked yetComplete 5 Kill Zombie Boss missions
Flush those zombies
Not unlocked yetDestroy 50 toilets
Fire in the hole!
Not unlocked yetThrow a grenade