Here is the full list of all 16 Zombie Town! achievements.
Complete a level without incurring any damage
Max out any upgrade on any character
Max out all 4 upgrades on any one character
Unlock all 5 weapons
Unlock Policeman character
Unlock Sheriff character
Unlock Samurai character
Unlock Agent character
Complete any 10 missions
Complete 5 Run For Your Life missions
Complete 5 Protect The Street missions
Complete 5 Collect Coins missions
Complete 5 Stay Alive missions
Complete 5 Kill Zombie Boss missions
Destroy 50 toilets
Throw a grenade