Requires: None. This is the default ending you get the first time you beat the game and whenever you don't meet the requirements for the other endings.
Description: Travis returns to his truck and resets his miles, which seems to symbolize him starting his life over. Alessa is seen through his mirror holding a baby (Cheryl). After the cutsceen you can hear the voices of Harry and his wife after they have found the baby (as seen in the beginning cutsceen of SH1).
Unlocks: Savior accolade, lonely moon gauntlets.
Bad
Requires: Second playthrough or later. You must kill at least 200 enemies.
Description: Travis is seen strapped down on a bed in a mental hospital. Travis hears the voices of people it seems he has murdered throughout the game. There are many theories on this ending, and it is currently unknown what is really going on here.
Unlocks: Butcher accolade, great cleaver.
Note: I will elaborate further on the theories of this ending and it's meaning at a later period.
UFO
Requires: Second playthrough or later. Unlock room 502 at the hotel with the key found on the second floor staircase in the alley north of the hospital (the same staircase you go up to fight the moth in SH1).
Description: This is an animated ending, like all the other ufo endings in Silent Hill. Travis tries to use the key to the hotel room, but it won't work. An alien and Mira (the SH2 Dog ending dog) show up in a UFO. Travis asks about his lost truck and they tell him it is on there planet and offer to take him there.
Unlocks: Ambassador accolade, tesla rifle.