Enter this for the following costume.

up, up, down, down, left, right, left, right, X, O Unlock the Codebreaker costume

Unlockables

Extra Options - In order to unlock extra options under the "Options" menu, simply beat the game once.

Run/Walk: Makes Travis Run by default.
More Blood: Makes the creatures spray more blood when attacked.
Noise Filter: Allows ability to turn off screen "Grain" effect making the graphics sharper.
Bloody Footprints: Travis will leave a footprint of blood with every step he takes.
Flashlight Filter: Change the light of the flashlight to a smiley face, soccer ball, jack-o-lantern or the mark of Samuel.

Unlockable Costumes - Complete the following.

Ambassador Get the UFO ending

Brawler Kill 50%+ of all enemies with only your fists
Butcher Get the Bad ending

Cartographer Looked at map less then 25 times
Codebreaker Do the Konami Code during your second playthough or up
Collector Collect more then 300 items

Daredevil Finish the game without saving

Explorer Distanced ran or walked greater then 22.5 km

Fireman Save Alessa in the beginning in less then 80 seconds

Night Vision Goggles Achieve the "Stalker" Accolade

Savior Finish the game once
Sharpshooter Kill 75%+ of all enemies with a firearm
Sprinter Finish game in under 2 hours
Stalker Use flashlight for less then 3 hours

Weaponsmith Kill 75%+ of all enemies with melee weapons

Unlockable Endings

Complete the following.

Bad Ending Kill 200 enemies for second time
Good Ending Beat the game for first time
UFO Ending Use Room 502 Key at the Motel Room

Unlockables

Fire Axe Recieved after getting the Fireman Accolade
Great Cleaver Get the Bad Ending
Moon Gauntlets Beat the game once.
Unlimited Rifle Get UFO Ending