Clock the game and then go to "Extra Costumes". Then enter these case-sensitive codes to unlock the relevant costume, which can be equipped during the game.
13eme Rue - Suspense
Block head - PutHere2FeelJoy
Don't Touch - TOUCH_MY_HEART
EGM Shirt - EGMpretaporter
Game Informer Tank Top - gameinformer
GamePro - ProTip
Gamereactor - SH3_Wrestlarn
GameSpy.com - iaml33t
GMR shirt - GMRownzjoo
GN - IwannabeaGJ
God of thunder - GangsterGirl
Golden Rooster - cockadooodledoo
Heather Shirt - HappyBirthDay
IGN.com Shirt - IGN_pickleboy
Killer rabbit - BlueRobbieWin
Official Playstation Magazine costume - SH3_OPiuM
Onsen - I_Love_You
OPS2 - extra_thumbs
Play - sLmLdGhSmKfBfH
PS2RO - MATADOR
PSM Tank Top - badical
Royal flush - 01_03_08_11_12
The light - LightToFuture
Transform - PrincessHeart
Transience - ShogyouMujou
Zipper - Shut_your_mouth
Book Store Puzzle Solution
Normal: 4 5 2 3 1
Hard: 8 3 5 2
Brookhaven Hospital 2nd Lobby Door Password
Normal: 8 6 3 4
Easy: 4 6 3 9
Hard: 4 8 9 6
Brookhaven Hospital 3rd Lobby Door Password
Normal: 4 7 5 6
Hard: 1 3 2 8
Brookhaven Hospital Crematory Solution
Hard: 9 2 7 1.
Brookhaven Hospital Suitcase Password
The password is simply whatever the time on the clock near the bed is. The code needs to be entered in 24 hour time, eg 6:30pm means 1 8 3 0.
Machine gun: hospital
Beam Saber: end of the hallway where you get the bookstore key, on the door.
Flamethrower: in Helen's bakery on the counter.
Infinite Ammo Machine Gun: right after you go out through the bathroom window (at the start of the game) turn left. The Gun is at the end of the dead end.
Silencer: after the sewer go to apartment 5F and you'll see a room with a large hole and a matress next to the hole. To the right of the matress is wall that has a light blue tinge to it. Bring the wall with a pipe here and you'll get the silencer.
Press LT, LB, RB or RT at the options screen to display an extra options menu.
Beginner Fighting Difficulty
If you die twice (like on purpose) while playing the game on normal fighting difficulty, then a beginner mode will be unlocked in the Extra Options menu.
Douglas in Boxers
Finish the game, then HIGHLIGHT "Extra New Game" at the main menu and press: Up, Up, Left, Right, Left, Right, B, A. Heather should then sigh once you choose a difficulty and riddle level. After this, in some scenes, Douglas will only be wearing boxers.
To get the UFO ending you need to first clock the game and unlock both the Princess Heart costume and the Heather Beam weapon. The Heather Beam can only be used if both Heather and Cheryl are not holding a weapon. Then when you play again, you need to kill all monsters and bosses using the Heather Beam.
To get the possessed ending, kill all monsters during the game with any weapon apart from melee weapons. Unlimited machine gun works well here!
Use Old Silent Hill 2 Save
If you have a completed saved game file from Silent Hill 2 while playing it in this version, you get new interactions with various objects and new scenes playing through again.
Unlock Life Display
Clock the game on hard and you will see an option to unlock the Life Display at the Extra Options menu.
Life display option
Successfully complete the game on the hard difficulty setting to unlock "Life Display" at the extra options screen.
Unlock Flamethrower, Beam Saber, Unlimited Machine Gun One Play Through
First you need to clock the game and save your results. This should give you one special weapon (either of the three listed above).
Then load the saved game again and finish it a second time. This should unlock the Flamethrower provided you didn't already have it.
Then do the same thing and finish it a third time, but make sure you kill the final boss, Claudio, using only melee wapons. Katana is best. This should unlock the Infinite Ammo Machine Gun for you. If you don't have the Beam Saber at this point, then only kill Claudia with long range weapons and you'll get that!
[more cheats for Silent Hill HD Collection here]