Press Up(2), Down(2), Left, Right, Left, Right, X, Circle at any time during your second or later replay.
In order to unlock extra options under the "Options" menu, simply beat the game once.
Beat game once & save. Reload game save & find room key 502. It is north of the hospital, up the long flight of stair's at the top of them. Play thru the game until you are at the Motel level. Use it to open the door & you will get the UFO ending. Save your game & reload it & the Tesla Rifle will be in your inventory.
Get the Butcher ending to unlock the Butcher's Cleaver. This is a powerful melee weapon which kills enemys instantly. However, you lose energy quickly as it is very big, so save some energy drinks in case you have to run.
In the place where Lisa tells you to go, you will eventually encounter a room with a circular object in the middle with three doors on the left, top, and right side of it. In this room, you might see invisible enemies wearing a mask of some sort. Look for the mask. It will always shine when you move your flashlight around.
The flashlight is useful for monsters detecting from afar, but it will make you noticeable. If you keep it turned off, you will be able to avoid monsters much easier. You can also sneak-attack them, even from a very close distance.
After you exit from the back door of the hospital, wander around a little bit to discover the health and energy drinks as well as other disposable weapons: a vase, 2x4, and a spike over by the bakery.
