At the "Extras" menu, select the "Credits" option, then scroll to the bottom of the screen to see something is hidden. Press Y(3), X(3), Y to unlock the Puzzle mini-game.Bubble gun
Start a game, and do not shoot for approximately two minutes while not getting damaged by the aliens to get the Bubble gun.Rainbow gun
Have your first shot kill a creature with one hit. Walk directly to its body, and wait at that location. Allow the other creatures to almost kill you to get the Rainbow gun. Note: This only works in earlier versions of the game.Completion bonuses
Successfully complete the game on the Normal difficulty to unlock Typ 'o' Shooter mode and the Hardcore difficulty.Alien Zoo Keeper mini-game
Watch the credits, and click all lines that have the letter "O". You will hear a sound with 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.Holiday message
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.Changing weapons at start
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 creature for a different weapon to appear. This will happen whenever you have the pistol and there are no other weapons on screen.Seven-way Plasma Gun
This trick allows you to use a "Seven-way Plasma Gun" and is useful in Survival mode. Acquire the Pulse Gun (that shoots little green waves). Get the following perks: Angry Reloader, Fastloader, and Stationary Reloader. Do not get the Perk Alternate weapon. After getting the gun and perks, hold [Reload]. Seven-way constant shots should start shooting from your weapon. Note: 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.Easy "Smart Pack Rat" achievement
There are two ways to collect 50 Blowtorches. For both, start a co-op game (recommended), solo if desired.
Play in Survival mode and go on a killing spree. Collect every weapon that is found.
Start a Quest mode map with monster nests (spawns). Have the second player join and survive until there is only one nest remaining. Go on a killing spree at regular intervals, and do not die. Use the Fire Cough perk to dispose of monsters easily without using big guns, which can destroy the nest. As long as one player still has the pistol, most kills should spawn weapons, as long as there are not any on screen. Kill as long as possible and eventually blowtorches will spawn. Note: Nests will eventually stop spawning monsters.
Accomplish the indicated achievement to get the corresponding number of Gamerscore points:
- Chapter 1 Complete (30 points): Complete all Quests in Chapter 1.
- Chapter 2 Complete (30 points): Complete all Quests in Chapter 2.
- Chapter 3 Complete (30 points): Complete all Quests in Chapter 3.
- Chapter 4 Complete (30 points): Complete all Quests in Chapter 4.
- Chapter 5 Complete (30 points): Complete all Quests in Chapter 5.
- Chapter 6 Complete (30 points): Complete all Quests in Chapter 6.
- Club Hardcore (80 points): Complete the game in Hardcore difficulty.
- Grim Reaper (200 points): Beat the game in Grim difficulty.
- Not a Scratch (30 points): Complete all Normal Quest levels with full health remaining.
- Impaler (30 points): Get 100 percent hit accuracy in Chapter 2 Quest 5.
- Smart Pack Rat (30 points): Collect 50 Blowtorches.
- Master of Chains (30 points): Bounce Shock Chain powerup over 30 times.
- Home Wrecker (30 points): Destroy over 500 nests.
- Bloody Good Time (30 points): Explode 50 creatures to gibs within the first 30 seconds of a level.
- Perky (50 points): Unlock all Perks.
- Little Survivor (30 points): Get over 250k points in Survival game mode.
- Mr Survivor (50 points): Get over 500k points in Survival game mode.
- Arms Race (50 points): Get over 100k points in Weapon Picker game mode.
- Feel the Rush (50 points): Get over 50k points in Rush game mode.
- Quickly! (50 points): Get over 250k points in Blitz game mode.
- Booom (50 points): Get over 75k points in Nukefism game mode.
- Chapter 7 Complete (30 points): Complete all Quests in Chapter 7.