Some of what I'm about to say has been said...but I can't help it:
KOTOR: The 'Past' reveal. Crazy. I didn't see it coming.
Baldur's Gate:
- Imoen being a Bhaal Spawn too. No WONDER there was no romance story with her! Creepy.
- Seravok and Kovares being one and the same. That dirty jerk.
- Khalid dying. I LOVED Khalid, and when I found his broken body (Granted, very early in the game) I was like 'awwwww dang'.
- Yoshimo betraying you. He was so freaking handy, too.
- Edwin finally getting his book of great power...and turning into a woman. Freaking hilarious.
BAD plot twists:
KOTOR 2: The old lady being bad. Who didn't see that coming?
And I sadly have to agree with the Fallout 3 ending. Pretty piss poor explanations of why Fawkes couldn't do it. It would have been better if there was some explosion and every died in the facility...BUT you, making you the only one who could have done it..instead of this 'destiny' crap.