You got that from a Top 10 list a few days back >_>
My favourite one would have to be the HUGE one from KotOR which you'll know what I'm talking about if I completed it (even if Vrook make it horribly obvious... I was young at the time so I didn't realise).
The World Ends With You ending was a great plot twist as well. ****ing Joshua. He's gotta be one of the biggest trolls in fictional character history. You meet him in week two, where he makes you think he's your enemy, then he makes you think he's your friend, then he makes you think he killed you, then he makes you think Sho killed you, then he makes you think he's dead, then in the cutscene, he lets you know he killed you, lets you know he was behind everything you've experienced the past three weeks, lets you know you were all part of a game and because you won Shibuya is destroyed... and then what does he do? He kills you again.... and he isn't even a boss fight ffs. I still <3 him though.
And Zelos betraying you in Tales of Symphonia. It wasn't necessarily mind-blowing, but Zelos was top-tier the entire cutscene.
Custom Robo had a pretty surprising twist in it too.
[Edited by fault2k, 7/22/2010 6:20:06 AM]