About Fallout 3

active pause — VATS functions like active pause even if it isn't exactly that; using the PipBoy also effectively pauses the game.
cannibalism — you meet current and "former" cannibals and can become one yourself by picking the "cannibal" perk.
auto-regen — there are at least two perks that give this under certain conditions, normally not present.
growing protagonist — goes through from birth to ages of 1, 10, 16 and 19. This effectively covers character creation completely and offers some backstory.
slavery — besides being somewhat common topic, player can also partake in this activity by stunning and collaring people (the collar will cause the slave's head to explode if they try to escape).

variable ending — the ending is constructed of 3 things: karma and two choices near the end that form total of around 10 "unique" endings (if minor details are ignored) constructed out of 28 video segments (see breakdown at Fallout wiki). Only around 4 endings if you play them out in very archetypical manner.

thx-1138 — the number is encountered at least in The Republic of Dave, unconfirmed reference.