Unlock the following Achievement Titles by performing the corresponding tasks:

ACHIEVEMENT TITLE - HOW TO UNLOCK
Bomber - Use 50 grenades.
Executioner - Get 200 head shots.
Game Cleared (Easy) - Beat all chapters on Easy.
Game Cleared (Hard) - Beat all chapters on Hard.
Game Cleared (Normal) - Beat all chapters on Normal.
Head Hunter - Get 100 head shots.
Head Shooter - Get 50 head shots.
Hunter Killer - Kill 100 Hunters.
Licker Killer - Kill 50 Lickers.
Put Trust In Others - Have your partner kill 30 enemies.
S.T.A.R.S. Mission - Beat the secret mission.
Trigger Happy - Fire more than 10,000 rounds.
Ultra-Rich - Collect 150,000 coins.
Wealthy - Collect 100,000 coins.
Well-Off - Collect 50,000 coins.
Zombie Hunter - Kill 500 zombies.
Zombie Killer - Kill 1,000 zombies.
Zombie Shooter - Kill 100 zombies.