ITT

you were actually a clone of the main character but not really

Prey?

The douche who stole your picnic was actually your deadbeat dad

The game was rigged from the start.

I cut back on funding and everything was fine

Tales of the Abyss
Eternal Darkness
Trails in the Sky

I'm here at the scene!
Hmm... Hmmhmm!
And dat ends my report from the scene!

Friends: The One with All the Trivia (2005)

Your father was a priest but he also killed your sister your mother and himself
The culprit of it all wasn't actually your father though, it was a teacher who is actually a immortal reincarnation of Lucifer
Your canon love interest is timid child that gets raped repeatedly by the principal but it's not actually rape because he imagines fucking you, but the actual twist is the pocket watch he carries around which is of his family who are dead, the reason for his entire timid personality and appearance is because he's jewish and was in death camps during the holocaust

You have toxoplasmosis

All one game
- There's a mountain she's trapped but when she escapes she sees a beach and sunset despite being on the top of a mountain, there's 3 personalities besides the two characters swapping, your other personality was killed by a alternate version of yourself, the little boy with you is a time traveller that's trying to prevent your death, you are trapped in a insane asylum and chased by a psycho killer but stuck in a man's body, you escape but the killer is never seen, that killer was actually you but wait your a culprit because of the security footage that happened meaning someone else took over your body, those people were infant children that were born inside a mine, the psycho girl that murdered 20 people in a hospital inhabits the facility but she's actually dead, she died in a avalanche but this isn't true because she's schizophrenic and eats a baby's heart in front of you meaning even her entire identity might be a lie, you see your love interest but she tells you that you aren't actually yourself and she doesn't recognize you meaning the entire game was a lie from the very beginning