To get an alternate costume for Yoko, play as Yoko complete the "Outbreak" stage under the normal difficulty setting. Once done, go to the "Collection" option at the main menu and choose "Costumes". Yoko's costume will cost 8,000 points. Once it is unlocked, you can play as Yoko before she changed into the person she is. Note: Yoko is the only character who has an alternate costume.
Cheat
Once finding the Frozen Wrench take it to the Break room and take it to the old rusty sink with warm water inside of it set this item in the sink it will thaw out take the wrench to the Laboratory where you find two maintinence panels and a yoko zombie you take the wrench too the panel on the far right and use it the panel will open revealing a valve which you use on the door that cannot be opened in the same room. Go up the ladder you will be a whole floor higher.
Defeating giant leech
On The Hive level, the Boss will be a giant leech. To kill it easily, make it chase you back to the start, where you first get on the boat. Once there, hop out of the water and shoot him (if you have ammunition). If you do not have ammunition you can use the steel pipe, broom, crutch, or knife to kill him. If you are using the knife, you can either hop back in, stand in front of the giant leech, then stab; or you can stand out of the water and use the knife. When you stand outside of the water you will not be able to hit the giant leech until it lifts up its head. You must then stab quickly; you should be able to get two or three stabs. If you are in the water fighting the giant leech, you can get a few good swings at it, but be careful -- it only shoots acid when it is stuck there. It also swings its head back and forth causing damage to your character. Note: Though this is a very easy way to kill the giant leech, you must also watch your partner's health. Your partner can die from the giant leech, and if that happens your partner will turn into a leechman.
Defeating Hunters
To kill Hunters easily, you can use a Magnum or do a team attack (this works offline and online). To use the team attack against the Hunters, have two people wait and have one as a decoy. For example, on the stage they appear on "Below Freezing Point", when you are in the West Passage area and the Hunter breaks free from the ice, it will stand there for a few seconds. Have two people wait around the corner and have one person run down the hall and back up towards the Hunter (not all the way in the doorway where the Hunter is located). Make enough room for him to pop out and around the corner. Once he is around the corner, have the two people who are waiting quickly run up and either start shooting or hitting it. The Hunter will have nowhere to go or have a chance to make an attack. This method works only for the stage "Below Freezing Point". Note: The only way you can get a Magnum is if you are playing as Yoko. Yoko gets the gun from a friend in the game, none of the other characters can get this gun.
Hard mode
Complete the "Decisions, Decisions" stage. You can now unlock hard mode for 2,000 points.
Hiding in lockers
You can hide from the monsters in lockers. For example, when in the "Outbreak" stage on the second floor and in the locker room, go to the last locker (next to the window). If you have a zombie chasing you and he happens to break down the door, hide in the locker. The zombie will look around, walk around in circles, then pound on the door to leave. Once he leaves, you can exit from the locker. Note: This works for all stages.
Hiding under tables or beds
If a zombie is entering and there are no lockers, go under the table or bed. Your character will sit there, and the camera view will change so that you can see the zombie's feet. Stay under the table or bed until you see the zombie leave.
Infinite ammo free mode
Complete all stages with a 100% rating. You can now unlock infinite ammo free mode for 50,000 points.
No Damage Clear
To get a "No Damage Clear" do not get attacked by any kind of monster. If you come close to a monster, use your special attack (R1 + X) or ram the monster (R1 + Circle). When a monster is coming close to you, call for help (Right Analog-stick Left) and the CPU character will arrive to help. If done correctly you will get about 4,000 points. Note: This is not an easy task. It is recommended that you play the game a few times then trying for a "No Damage Clear".
No Weapon Clear
To get points for a "No Weapon Clear", pass any weapons you find to the CPU. You cannot use any weapons/ You can pick them up and combine items for the CPU, but you can never use a weapon. You can use your special attack (R1 + X) and the characters will punch or kick the monster. You can also ram the monsters (R1 + Circle) . You also can use health items if needed for you or your CPU characters. Note: Only Kevin, David, Mark, and George can punch, kick, and tackle.
Obtain all items
To get an even better score, obtain all items in the stage. You must collect files, useless items (such as diaries and test tubes), press buttons, etc. This will boost your points. Note: Collecting the items can clog up your inventory spaces. You can pass the items to your CPU characters to keep until the end of the stage.
Obtain the "Daylight" virus
In the stage "Decisions, Decisions", collect an extra tube of "Daylight" virus and you will get a different ending and points. Note: When getting the extra "Daylight", do not use it. Keep it in your inventory for the
different ending and points.
Play as fire fighter or policeman
To play as a fire fighter or policeman, complete the stages "Outbreak" and "Hell Fire" with any charter. Once done, go to the "Collection" option at the main menu and choose "Costumes". Both of those costumes cost 5,000 points. After unlocking them, they can be used on any stage. Note: They are Kevin and Mark's other costumes. When playing as either a fire fighter or policeman, they will have Kevin and Mark's storylines and voice effects.
Play as Frank
To play as Frank you must complete the stage "Decisions, Decisions" under the hard difficulty setting. Once this is done, go to the "Collection" option at the main menu and choose "Costumes". You will need 8,000 points to unlock him. Note: When playing as Frank he will have Jim's storyline.
Play As Hunk In Single Player
Go through entire online scenario and single player missions, receive the helicopter ending, save, at menu screen highlight New Game and press Square (2), Triangle (2), Square (2), Triangle (3) to play as Hunk in single player mission. Hunk has first aid spray in inventory.
Play as match stick men
To play as match stick men you must complete all stages under easy, normal, hard, and very hard difficulty settings. You must also unlock all secrets in the game. Once done, go to the "Collection" option at the main menu and choose "Extras". Match stick men will cost 100,000 points to unlock. Note: Once the match stick men are unlocked, they will have Kevin's, David's, Jim's, Mark's, and George's storylines.
Play as Monica
To play as Monica from the stage "Below Freezing Point" you must first complete the stage as any character. Once done, go to the "Collection" option at the main menu and choose "Costumes". Her costume costs 5,000 points, Once unlocked you can play as Monica on any stage. Note: This is one of Alyssa's costumes; Monica will have Alyssa's voice effect.
Play as Peter
To play as Peter (George's friend), you must complete the stage "Decisions, Decisions" under the hard difficulty setting. Once this is done, go to the "Collection" option at the main menu and choose "Costumes". You must have 5,000 points in order to unlock Peter as a playable charater. Note: Peter will have George's storyline.
S.W.A.T. Major Guns and Ammo
On the scenario Outbreak once you are outside the swat car get back in and take 3 shot guns and present two of the to your partners once this is done pick up any items wanted from the car you will find a magnum and many bullets if you have dropped any items in the swat car and leave them they will not be available when you come back to get them. The reason you give two shotguns to your CPU's is because they will protect you at the end while you are finding the detenator pieces.
Secret FMV sequence
On the stage "Below Freezing Point" there is a secret FMV sequence. To view it, you must do the following. After using the V-Jolt on the plant go up to level B-4 (skip level B-5 for now). Once on B-4, go past the frozen Hunter and pick up the herb and pipe in the back. Then, go back to level B-6 (again skipping level B-5) and enter the keycodes into the main computer system. Make sure to enter the word "HOPE". Then, go to level B-5 and go through the vents. Be careful as a zombie will be here under the normal, hard, and very hard difficulty settings. Once through, go to the key panel, open the shutter, and enter the computer room. Then, enter your fingerprint into the computer. Finally, go back to level B-4 and go through the only open door. If done correctly, you will unlock the secret FMV sequence of your character getting attacked by the giant moth. Note: After the FMV sequence ends, you will be back in the computer room attached to the wall, and you must struggle to get out. This will cause your health to be in "Poison" status.
Solo mode
Complete all stages in hard mode. You can now unlock very hard mode for 10,000 points.
Stopping your virus meter
There are two ways to stop your virus meter from going up. The first way is to use the Anti-Virus Pill. This will stop the meter until you are attacked again. The other way is to use a Red Herb. This will stop the meter for a few minutes.
Using the hiding feature
Try the following tricks to use the hiding feature to your advantage. Note: Do not to talk, look at your map, or open your menu screen, as this will blow your cover and the zombie or other monsters will cause damage to your character.
Very hard mode
Complete all stages in hard mode. You can now unlock very hard mode for 3,000 points.
Yoko: Costume B
Collect the following SP Items: Cute Sneakers, Green One-Piece Dress.