Change Weapons in Survival Mode:
When you kill your first or second creature in Survival mode they will always have a new weapon power-up. If this weapon is not to your liking you can change it by remaining idle so that it disappears and then kill another creature so you get a different weapon power-up. This will happen whenever you have the pistol and there are no other weapons on screen.
Alien Zoo Keeper mini-game
Watch the credits and click all lines that have the letter "O". A sound will confirm each correct click. When the name list ends, wait and another list will begin. Once again, click the lines that have the letter "O". The word "Secrets" will appear. Click it to play the Alien Zoo Keeper mini game.
Unlock Puzzle mini-game:
If you select the 'Credits' option at the 'Extras' menu and scroll to the bottom of the screen you will be able to see something is hidden. If you now press Triangle(3), Square(3), Triangle the Puzzle mini-game will become unlocked.
Start a game and do not shoot for about two minutes while not getting damaged by the aliens.
Change weapon at the beginning
In survival mode the first or second creature you kill will always have a new weapon power-up. If you do not like that weapon, just wait for it to disappear and kill another zombie for a different weapon to appear. This will happen whenever you have the pistol and there are no other weapons on screen.
Successfully complete the game under the normal difficulty setting to unlock the hardcore difficulty setting and Typ 'o' Shooter mode.
Set the system date to December 25. When the game starts, a "Happy Holiday" message will appear with snow. Click on the snow or message to return to normal.
Have your first shot kill an alien with one hit. Walk directly to its body and wait at that location. Allow the other aliens to almost kill you to get the gun. Note: This only works in earlier versions of the game.
Seven way Plasma Gun
This trick allows you to use a "7-way Plasma Gun" and is useful in survival mode. Acquire the Pulse Gun (that shoots little green waves). Get these Perks: Angry Reloader, Fastloader, and Stationary Reloader. Do not get the Perk Alternate Weapon, as this will mess things up. After getting the gun and Perks, hold [Reload]. Seven-way constant shots should start spewing from your weapon. Note: Do not get the Perk Alternate Weapon. Remain still if you have Stationary Reloader and the shots will fire faster. Try this with the "Weapon Power-up". Barrel Greaser and Fastshot will make the shots go faster, but not more frequently.
Complete the following tasks to unlock PlayStation 4 trophy rewards.
Trophy How to unlock
Arms Race (Bronze) Get over 100k points in Weapon Picker game mode.
Bloody Good Time (Bronze) Explode 50 creatures to gibs within the first 30 seconds of a level.
Booom (Bronze) Get over 75k points in Nukefism game mode.
Chapter 1 Complete (Bronze) Complete all Quests in Chapter 1.
Chapter 2 Complete (Bronze) Complete all Quests in Chapter 2.
Chapter 3 Complete (Bronze) Complete all Quests in Chapter 3.
Chapter 4 Complete (Bronze) Complete all Quests in Chapter 4.
Chapter 5 Complete (Bronze) Complete all Quests in Chapter 5.
Chapter 6 Complete (Bronze) Complete all Quests in Chapter 6.
Club Hardcore (Bronze) Complete the game in Hardcore difficulty.
Feel the Rush (Bronze) Get over 50k points in Rush game mode.
Grim Reaper (Bronze) Beat the game in Grim difficulty.
Home Wrecker (Bronze) Destroy over 500 nests.
Impaler (Bronze) Get 100 percent hit accuracy in Chapter 2 Quest 5.
Little Survivor (Bronze) Get over 250k points in Survival game mode.
Master of Chains (Bronze) Bounce Shock Chain powerup over 30 times.
Mr Survivor (Bronze) Get over 500k points in Survival game mode.
Not a Scratch (Bronze) Complete all Normal Quest levels with full health remaining.
Perky (Bronze) Unlock all Perks.
Quickly! (Bronze) Get over 250k points in Blitz game mode.
Smart Pack Rat (Bronze) Collect 50 Blowtorches.