Location not disclosed
Get 500 balls!
Blow up 300 rocks!
Play the game for 15 minutes!
Go through the whole intro without skipping.
Weaken a hood grappling zombie with 1 weapon, then quickly switch to another weapon to finish it off with one shot
Kill 3000 enemies in total.
Get a score of 500,000 in any level except survival.
Get A ranks in 10 or more levels.
Get killed with no enemies on screen.
Get A ranks in 5 or more levels.