SPOILER WARNING: this gives away the opening of the game, in case you were worried about stuff like that.
Even though Far Cry 4 isn't even out yet, people have figured out one of the more ridiculous secrets of the game.
After your introduction to this Far Cry's version of Vaas, named Pagan Min and SLIGHTLY more in control of his faculties, you're left alone at a dinner table, with the expectation that you'll wander off and begin your adventure through the land of Kyrat. However, if you DON'T leave the table and just sit amiably (as you were asked to do) for about 10 minutes, this happens (skip to about 10:30 to get to the secret ending-y stuff):
Pagan Min returns, and is happy to see you HAVEN'T behaved like most videogame protagonists with free will.
Afterwards, Pagan Min gives you a helicopter ride to the spot where your mother asked you to spread her ashes...
...a shrine to your departed half-sister, who you never knew you had (and who is the daughter of Pagan Min). You place your mother's ashes in the shrine, get back on the helicopter with Pagan Min, and roll credits - it's game over.
Of course, you don't get to ride elephants in this version, so it's not recommended.